openapi: 3.1.0
info:
title: Fireworks AI Anthropic Compatible Messages anthropic-messages.openapi_other Chat API
description: Anthropic-compatible Messages API endpoint for Fireworks AI inference
version: 1.0.0
servers:
- url: https://api.fireworks.ai/inference
security:
- BearerAuth: []
tags:
- name: Chat
paths:
/v1/chat/completions:
post:
summary: Create Chat Completion
description: 'Create a completion for the provided prompt and parameters.
For RL / agent rollouts, Fireworks inference exposes additional
rollout-specific features:
[`x-session-affinity` and `x-multi-turn-session-id`](https://docs.fireworks.ai/guides/rollout-inference#session-affinity)
for multi-turn trajectories, and
[MoE Router Replay (R3)](https://docs.fireworks.ai/guides/rollout-inference#moe-router-replay)
for MoE expert tracing during rollouts.'
operationId: create_chat_completion_v1_chat_completions_post
requestBody:
content:
application/json:
schema:
$ref: '#/components/schemas/ChatCompletionRequest'
required: true
responses:
'200':
description: Successful Response
content:
application/json:
schema:
$ref: '#/components/schemas/ChatCompletionResponse'
text/event-stream:
schema:
$ref: '#/components/schemas/ChatCompletionStreamResponse'
'422':
description: Validation Error
content:
application/json:
schema:
$ref: '#/components/schemas/HTTPValidationError'
tags:
- Chat
components:
schemas:
LogProbs:
additionalProperties: false
description: Legacy log probabilities format
properties:
tokens:
items:
type: string
title: Tokens
type: array
token_logprobs:
items:
type: number
title: Token Logprobs
type: array
top_logprobs:
anyOf:
- items:
additionalProperties:
type: number
type: object
type: array
- type: 'null'
title: Top Logprobs
text_offset:
items:
type: integer
title: Text Offset
type: array
token_ids:
anyOf:
- items:
type: integer
type: array
- type: 'null'
default: null
title: Token Ids
title: LogProbs
type: object
NewLogProbs:
additionalProperties: false
description: OpenAI-compatible log probabilities format
properties:
content:
items:
$ref: '#/components/schemas/NewLogProbsContent'
title: Content
type: array
title: NewLogProbs
type: object
ValidationError:
properties:
loc:
items:
anyOf:
- type: string
- type: integer
type: array
title: Location
msg:
type: string
title: Message
type:
type: string
title: Error Type
input:
title: Input
ctx:
type: object
title: Context
type: object
required:
- loc
- msg
- type
title: ValidationError
RawOutput:
additionalProperties: false
description: 'Extension of OpenAI that returns low-level interaction of what the model
sees, including the formatted prompt and function calls'
properties:
prompt_fragments:
description: Pieces of the prompt (like individual messages) before truncation and concatenation. Depending on prompt_truncate_len some of the messages might be dropped. Contains a mix of strings to be tokenized and individual tokens (if dictated by the conversation template)
items:
anyOf:
- type: string
- type: integer
title: Prompt Fragments
type: array
prompt_token_ids:
description: Fully processed prompt as seen by the model
items:
type: integer
title: Prompt Token Ids
type: array
completion:
description: Raw completion produced by the model before any tool calls are parsed
title: Completion
type: string
completion_token_ids:
anyOf:
- items:
type: integer
type: array
- type: 'null'
default: null
description: Token IDs for the raw completion
title: Completion Token Ids
completion_logprobs:
anyOf:
- $ref: '#/components/schemas/NewLogProbs'
- type: 'null'
default: null
description: Log probabilities for the completion. Only populated if logprobs is specified in the request
images:
anyOf:
- items:
type: string
type: array
- type: 'null'
default: null
description: Images in the prompt
title: Images
videos:
anyOf:
- items:
type: string
type: array
- type: 'null'
default: null
description: Videos in the prompt
title: Videos
grammar:
anyOf:
- type: string
- type: 'null'
default: null
description: Grammar used for constrained decoding, can be either user provided (directly or JSON schema) or inferred by the chat template
title: Grammar
required:
- prompt_fragments
- prompt_token_ids
- completion
title: RawOutput
type: object
ThinkingConfigDisabled:
properties:
type:
type: string
const: disabled
title: Type
additionalProperties: false
type: object
required:
- type
title: ThinkingConfigDisabled
description: Configuration for disabling extended thinking (Anthropic-compatible format).
ChatCompletionStreamResponse:
additionalProperties: false
description: The streamed response message from a /v1/chat/completions call.
properties:
id:
description: A unique identifier of the response
title: Id
type: string
object:
default: chat.completion.chunk
description: The object type, which is always "chat.completion.chunk"
title: Object
type: string
created:
description: The Unix time in seconds when the response was generated
title: Created
type: integer
model:
description: The model used for the chat completion
title: Model
type: string
choices:
description: The list of streamed chat completion choices
items:
$ref: '#/components/schemas/ChatCompletionResponseStreamChoice'
title: Choices
type: array
usage:
anyOf:
- $ref: '#/components/schemas/UsageInfo'
- type: 'null'
default: null
perf_metrics:
anyOf:
- additionalProperties: true
type: object
- type: 'null'
default: null
description: See parameter [perf_metrics_in_response](#body-perf-metrics-in-response)
title: Perf Metrics
prompt_token_ids:
anyOf:
- items:
type: integer
type: array
- type: 'null'
default: null
description: Token IDs for the prompt (when return_token_ids=true, sent in first chunk)
title: Prompt Token Ids
required:
- id
- created
- model
- choices
title: ChatCompletionStreamResponse
type: object
PredictedOutput:
properties:
content:
anyOf:
- type: string
- items:
$ref: '#/components/schemas/ChatMessageContent'
type: array
title: Content
type:
type: string
const: content
title: Type
default: content
additionalProperties: false
type: object
required:
- content
title: PredictedOutput
description: OpenAI-compatible struct for the "speculation" field.
ChatMessageContentImageURL:
properties:
url:
type: string
title: Url
detail:
anyOf:
- type: string
- type: 'null'
title: Detail
additionalProperties: false
type: object
required:
- url
title: ChatMessageContentImageURL
ChatCompletionFunction:
properties:
name:
type: string
title: Name
description: The name of the function to be called. Must be a-z, A-Z, 0-9, or contain underscores and dashes, with a maximum length of 64.
description:
anyOf:
- type: string
- type: 'null'
title: Description
description: A description of what the function does, used by the model to choose when and how to call the function.
parameters:
additionalProperties: true
type: object
title: Parameters
description: "The parameters the function accepts, described as a JSON Schema object.\n\nThe JSON Schema object should have the following structure:\n\n```json\n{\n \"type\": \"object\",\n \"required\": [\"param1\", \"param2\"],\n \"properties\": {\n \"param1\": {\n \"type\": \"string\",\n \"description\": \"...\"\n },\n \"param2\": {\n \"type\": \"number\",\n \"description\": \"...\"\n }\n }\n}\n```\n\n- The `type` field must be `\"object\"`.\n- The `required` field is an array of strings indicating which parameters are required.\n- The `properties` field is a map of property names to their definitions, where each property is an object with `type` (string) and `description` (string) fields.\n\nTo describe a function that accepts no parameters, provide the value:\n\n```json\n{\"type\": \"object\", \"properties\": {}}\n```"
strict:
anyOf:
- type: boolean
- type: 'null'
title: Strict
additionalProperties: false
type: object
required:
- name
title: ChatCompletionFunction
DeltaMessage:
additionalProperties: false
description: A message delta.
properties:
role:
anyOf:
- type: string
- type: 'null'
default: null
description: The role of the author of this message
title: Role
content:
anyOf:
- type: string
- type: 'null'
default: null
description: The contents of the chunk message
title: Content
reasoning_content:
anyOf:
- type: string
- type: 'null'
default: null
description: The reasoning or thinking process generated by the model. This field is only available for certain reasoning models (GLM 4.5, GLM 4.5 Air, GPT OSS 120B, GPT OSS 20B) and contains the model's internal reasoning that would otherwise appear in `<think></think>` tags within the content field.
title: Reasoning Content
tool_calls:
anyOf:
- items:
$ref: '#/components/schemas/ChatCompletionMessageToolCall'
type: array
- type: 'null'
default: null
title: Tool Calls
title: DeltaMessage
type: object
ChatCompletionTool:
properties:
type:
type: string
enum:
- function
title: Type
description: The type of the tool. Currently, only `function` is supported.
function:
anyOf:
- $ref: '#/components/schemas/ChatCompletionFunction'
- type: 'null'
description: Required for function tools.
additionalProperties: false
type: object
required:
- type
title: ChatCompletionTool
NewLogProbsContent:
additionalProperties: false
properties:
token:
title: Token
type: string
logprob:
title: Logprob
type: number
sampling_logprob:
anyOf:
- type: number
- type: 'null'
title: Sampling Logprob
bytes:
items:
type: integer
title: Bytes
type: array
top_logprobs:
items:
$ref: '#/components/schemas/NewLogProbsContentTopLogProbs'
title: Top Logprobs
type: array
token_id:
title: Token Id
type: integer
text_offset:
title: Text Offset
type: integer
last_activation:
anyOf:
- type: string
- type: 'null'
default: null
title: Last Activation
routing_matrix:
anyOf:
- type: string
- type: 'null'
default: null
title: Routing Matrix
required:
- token
- logprob
- sampling_logprob
- bytes
- token_id
- text_offset
title: NewLogProbsContent
type: object
PromptTokensDetails:
additionalProperties: false
properties:
cached_tokens:
anyOf:
- type: integer
- type: 'null'
default: null
title: Cached Tokens
title: PromptTokensDetails
type: object
ChatCompletionResponse:
additionalProperties: false
description: The response message from a /v1/chat/completions call.
properties:
id:
description: A unique identifier of the response
title: Id
type: string
object:
default: chat.completion
description: The object type, which is always "chat.completion"
title: Object
type: string
created:
description: The Unix time in seconds when the response was generated
title: Created
type: integer
model:
description: The model used for the chat completion
title: Model
type: string
choices:
description: The list of chat completion choices
items:
$ref: '#/components/schemas/ChatCompletionResponseChoice'
title: Choices
type: array
usage:
anyOf:
- $ref: '#/components/schemas/UsageInfo'
- type: 'null'
default: null
perf_metrics:
anyOf:
- additionalProperties: true
type: object
- type: 'null'
default: null
description: See parameter [perf_metrics_in_response](#body-perf-metrics-in-response)
title: Perf Metrics
prompt_token_ids:
anyOf:
- items:
type: integer
type: array
- type: 'null'
default: null
description: Token IDs for the prompt (when return_token_ids=true)
title: Prompt Token Ids
required:
- id
- created
- model
- choices
title: ChatCompletionResponse
type: object
FunctionNameSpec:
properties:
name:
type: string
title: Name
additionalProperties: false
type: object
required:
- name
title: FunctionNameSpec
ChatMessageContentVideoURL:
properties:
url:
type: string
title: Url
detail:
anyOf:
- type: string
- type: 'null'
title: Detail
max_frames:
anyOf:
- type: integer
- type: 'null'
title: Max Frames
spatial_limit:
anyOf:
- type: integer
- type: 'null'
title: Spatial Limit
sample_fps:
anyOf:
- type: number
- type: 'null'
title: Sample Fps
additionalProperties: false
type: object
required:
- url
title: ChatMessageContentVideoURL
ChatCompletionRequest:
properties:
model:
type: string
title: Model
description: 'The name of the model to use.
Example: `"accounts/fireworks/models/kimi-k2-instruct-0905"`'
messages:
items:
$ref: '#/components/schemas/ChatMessage'
type: array
title: Messages
description: A list of messages comprising the conversation so far.
tools:
items:
$ref: '#/components/schemas/ChatCompletionTool'
type: array
title: Tools
description: 'A list of tools the model may call. Currently, only functions are supported as a tool.
Use this to provide a list of functions the model may generate JSON inputs for.
See the our [model library](https://app.fireworks.ai/models/?filter=LLM&functionCalling=true) for the list of supported models'
tool_choice:
anyOf:
- type: string
enum:
- auto
- none
- any
- required
- $ref: '#/components/schemas/FunctionSelection'
title: Tool Choice
description: "Controls which (if any) tool is called by the model.\n\n- `none`: the model will not call any tool and instead generates a message.\n- `auto`: the model can pick between generating a message or calling one or more tools.\n- `required` (alias: `any`): the model must call one or more tools.\n To force a specific function, pass an object of the form `{ \"type\": \"function\", \"name\": \"my_function\" }` or `{ \"type\": \"function\", \"function\": { \"name\": \"my_function\" } }` for OpenAI compatibility."
default: auto
stream:
anyOf:
- type: boolean
- type: 'null'
title: Stream
description: 'Whether to stream back partial progress. If set, tokens will be sent as data-only [server-sent events](https://developer.mozilla.org/en-US/docs/Web/API/Server-sent_events/Using_server-sent_events#Event_stream_format) as they become available, with the stream terminated by a `data: [DONE]` message.'
default: false
response_format:
anyOf:
- $ref: '#/components/schemas/ResponseFormat'
- type: 'null'
description: 'Allows to force the model to produce specific output format.
Setting to `{ "type": "json_object" }` enables JSON mode, which guarantees the message the model generates is valid JSON.
If `"type"` is `"json_schema"`, a JSON schema must be provided. E.g., `response_format = {"type": "json_schema", "json_schema": <json_schema>}`.
Important: when using JSON mode, it''s crucial to also instruct the model to produce JSON via a system or user message. Without this, the model may generate an unending stream of whitespace until the generation reaches the token limit, resulting in a long-running and seemingly "stuck" request.
Also note that the message content may be partially cut off if `finish_reason="length"`, which indicates the generation exceeded `max_tokens` or the conversation exceeded the max context length. In this case the return value might not be a valid JSON.'
temperature:
anyOf:
- type: number
- type: 'null'
title: Temperature
description: 'What sampling temperature to use, between 0 and 2. Higher values like 0.8 will make the output more random, while lower values like 0.2 will make it more focused and deterministic.
We generally recommend altering this or top_p but not both.
Required range: `0 <= x <= 2`
Example: `1`'
top_k:
anyOf:
- type: integer
- type: 'null'
title: Top K
description: 'Top-k sampling is another sampling method where the k most probable next tokens are filtered and the probability mass is redistributed among only those k next tokens. The value of k controls the number of candidates for the next token at each step during text generation. Must be between 0 and 100.
Required range: `0 <= x <= 100`
Example: `50`'
user:
anyOf:
- type: string
- type: 'null'
title: User
description: A unique identifier representing your end-user, which can help monitor and detect abuse.
prompt_cache_key:
anyOf:
- type: string
- type: 'null'
title: Prompt Cache Key
description: A key used for prompt caching session affinity. Requests with the same prompt_cache_key are routed to the same backend to maximize KV cache hit rates. This is the preferred field for session affinity (takes priority over the 'user' field).
prompt_cache_isolation_key:
anyOf:
- type: string
- type: 'null'
title: Prompt Cache Isolation Key
description: Isolation key for prompt caching to separate cache entries.
raw_output:
anyOf:
- type: boolean
- type: 'null'
title: Raw Output
description: Return raw output from the model.
default: false
perf_metrics_in_response:
anyOf:
- type: boolean
- type: 'null'
title: Perf Metrics In Response
description: 'Whether to include performance metrics in the response body.
**Non-streaming requests:** Performance metrics are always included in response headers (e.g., `fireworks-prompt-tokens`, `fireworks-server-time-to-first-token`). Setting this to `true` additionally includes the same metrics in the response body under the `perf_metrics` field.
**Streaming requests:** Performance metrics are only included in the response body under the `perf_metrics` field in the final chunk (when `finish_reason` is set). This is because headers may not be accessible during streaming.
The response body `perf_metrics` field contains the following metrics:
**Basic Metrics (all deployments):**
- `prompt-tokens`: Number of tokens in the prompt
- `cached-prompt-tokens`: Number of cached prompt tokens
- `server-time-to-first-token`: Time from request start to first token (in seconds)
- `server-processing-time`: Total processing time (in seconds, only for completed requests)
**Predicted Outputs Metrics:**
- `speculation-prompt-tokens`: Number of speculative prompt tokens
- `speculation-prompt-matched-tokens`: Number of matched speculative prompt tokens (for completed requests)
**Dedicated Deployment Only Metrics:**
- `speculation-generated-tokens`: Number of speculative generated tokens (for completed requests)
- `speculation-acceptance`: Speculation acceptance rates by position
- `backend-host`: Hostname of the backend server
- `num-concurrent-requests`: Number of concurrent requests
- `deployment`: Deployment name
- `tokenizer-queue-duration`: Time spent in tokenizer queue
- `tokenizer-duration`: Time spent in tokenizer
- `prefill-queue-duration`: Time spent in prefill queue
- `prefill-duration`: Time spent in prefill
- `generation-queue-duration`: Time spent in generation queue
- `generation-duration`: Time spent in generation'
default: false
n:
type: integer
title: N
description: 'How many completions to generate for each prompt.
**Note:** Because this parameter generates many completions, it can quickly consume your token quota. Use carefully and ensure that you have reasonable settings for `max_tokens` and `stop`.
Required range: `1 <= x <= 128`
Example: `1`'
default: 1
service_tier:
type: string
enum:
- auto
- default
- flex
- priority
title: Service Tier
description: The service tier to use for the request. Specifies the processing type used for serving the request. Only "priority" is supported, while all other values will be treated as "default" tier.
default: default
stop:
anyOf:
- type: string
- items:
type: string
type: array
- type: 'null'
title: Stop
description: Up to 4 sequences where the API will stop generating further tokens. The returned text will NOT contain the stop sequence.
max_tokens:
anyOf:
- type: integer
- type: 'null'
title: Max Tokens
description: The maximum number of tokens to generate in the completion. If the token count of your prompt plus max_tokens exceeds the model's context length, the behavior depends on context_length_exceeded_behavior. By default, max_tokens will be lowered to fit in the context window instead of returning an error.
max_completion_tokens:
anyOf:
- type: integer
- type: 'null'
title: Max Completion Tokens
description: Alias for max_tokens. Cannot be specified together with max_tokens.
top_p:
anyOf:
- type: number
- type: 'null'
title: Top P
description: 'An alternative to sampling with temperature, called nucleus sampling, where the model considers the results of the tokens with top_p probability mass. So 0.1 means only the tokens comprising the top 10% probability mass are considered.
We generally recommend altering this or temperature but not both.
Required range: `0 <= x <= 1`
Example: `1`'
min_p:
anyOf:
- type: number
- type: 'null'
title: Min P
description: 'Minimum probability threshold for token selection. Only tokens with probability >= min_p are considered for selection. This is an alternative to `top_p` and `top_k` sampling.
Required range: `0 <= x <= 1`'
typical_p:
anyOf:
- type: number
- type: 'null'
title: Typical P
description: 'Typical-p sampling is an alternative to nucleus sampling. It considers the most typical tokens whose cumulative probability is at most typical_p.
Required range: `0 <= x <= 1`'
frequency_penalty:
anyOf:
- type: number
- type: 'null'
title: Frequency Penalty
description: 'Number between -2.0 and 2.0. Positive values penalize new tokens based on their existing frequency in the text so far, decreasing the model''s likelihood to repeat the same line verbatim.
Reasonable value is around 0.1 to 1 if the aim is to just reduce repetitive samples somewhat. If the aim is to strongly suppress repetition, then one can increase the coefficients up to 2, but this can noticeably degrade the quality of samples. Negative values can be used to increase the likelihood of repetition.
See also `presence_penalty` for penalizing tokens that have at least one appearance at a fixed rate.
OpenAI compatible (follows OpenAI''s conventions for handling token frequency and repetition penalties).
Required range: `-2 <= x <= 2`'
presence_penalty:
anyOf:
- type: number
- type: 'null'
title: Presence Penalty
description: 'Number between -2.0 and 2.0. Positive values penalize new tokens based on whether they appear in the text so far, increasing the model''s likelihood to talk about new topics.
Reasonable value is around 0.1 to 1 if the aim is to just reduce repetitive samples somewhat. If the aim is to strongly suppress repetition, then one can increase the coefficients up to 2, but this can noticeably degrade the quality of samples. Negative values can be used to increase the likelihood of repetition.
See also `frequency_penalty` for penalizing tokens at an increasing rate depending on how often they appear.
OpenAI compatible (follows OpenAI''s conventions for handling token frequency and repetition penalties).
Required range: `-2 <= x <= 2`'
repetition_penalty:
anyOf:
- type: number
- type: 'null'
title: Repetition Penalty
description: 'Applies a penalty to repeated tokens to discourage or encourage repetition. A value of `1.0` means no penalty, allowing free repetition. Values above `1.0` penalize repetition, reducing the likelihood of repeating tokens. Values between `0.0` and `1.0` reward repetition, increasing the chance of repeated tokens. For a good balance, a value of `1.2` is often recommended. Note that the penalty is applied to both the generated output and the prompt in decoder-only models.
Required range: `0 <= x <= 2`'
mirostat_target:
anyOf:
- type: number
- type: 'null'
title: Mirostat Target
description: 'Defines the target perplexity for the Mirostat algorithm. Perplexity measures the unpredictability of the generated text, with higher values encouraging more diverse and creative outputs, while lower values prioritize predictability and coherence. The algorithm dynamically adjusts the token selection to maintain this target during text generation.
If not specified, Mirostat sampling is disabled.'
mirostat_lr:
anyOf:
- type: number
- type: 'null'
title: Mirostat Lr
description: Specifies the learning rate for the Mirostat sampling algorithm, which controls how quickly the model adjusts its token distribution to maintain the target perplexity. A smaller value slows down the adjustments, leading to more stable but gradual shifts, while higher values speed up corrections at the cost of potential instability.
seed:
anyOf:
- type: integer
- type: 'null'
title: Seed
description: Random seed for deterministic sampling.
logprobs:
anyOf:
- type: integer
- type: boolean
- type: 'null'
title: Logprobs
description: 'Include log probabilities in the response. This accepts either a boolean or an integer:
If set to `true`, log probabilities are included and the number of alternatives can be controlled via `top_logprobs` (OpenAI-compatible behavior).
If set to an integer N (0-5), include log probabilities for up to N most likely tokens per position in the legacy format.
The API will always return the logprob of the sampled token, so there may be up to `logprobs+1` elements in the response when an integer is used. The maximum value for the integer form is 5.'
top_logprobs:
anyOf:
- type: integer
- type: 'null'
title: Top Logprobs
description: 'An integer between 0 and 5 specifying the number of most likely tokens to return at each token position, each with an associated log probability. The minimum value is 0 and the maximum value is 5.
When `logprobs` is set, `top_logprobs` can be used to modify how many top log probabilities are returned. If `top_logprobs` is not set, the API will return up to `logprobs` tokens per position.
Required range: `0 <= x <= 5`'
echo:
anyOf:
- type: boolean
- type: 'null'
title: Echo
description: Echo back the prompt in addition to the completion.
default: false
echo_last:
anyOf:
- type: integer
- type: 'null'
title: Echo Last
description: Echo back the last N tokens of the prompt in addition to the completion. This is useful for obtaining logprobs of the prompt suffix but without transferring too much data. Passing `echo_last=len(prompt)` is the same as `echo
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