Blink Messages API
Send, read, edit and delete messages within a chat.
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OpenAPI Specification
openapi: 3.2.0
info:
title: Blink Chat Messages API
version: 1.1.0
description: 'The Blink Chat API lets integrations create and manage chats, control who has access to them and who is in them, and send, read, edit, react to and delete messages on behalf of an app.
## Concepts
All calls are made from an **app identity**; every endpoint acts on behalf of that app.
A **chat** is a **private** thread of communication: the users and apps individually granted access to it take part, and nobody else.
**Access and membership are separate.** *Access* is permission to be in a chat, given by a **grant** and listed in the chat''s **grants** collection. *Membership* is whether a principal has actually joined: members appear in the chat''s member listing and the chat reaches their inbox.
The two usually move together — granting a user or app access also joins them, and revoking it removes them — but membership can change on its own: a member may leave, or be removed by an administrator, while keeping their grant, and may then rejoin with `:join`.
A **member** is a user or app currently in a chat. Each member carries their `role` (`admin` or `member`), their `membership` state, and `access_via`, the grant giving them access. The caller''s own row comes back with an `@type` of `me` and carries the favourite flag and inbox state that belong to them alone.
A **message** carries a structured **body** (Markdown, and other variants), an optional set of file **attachments**, a **sender**, and any **reactions** recorded against it.
**Attachments** - message files and chat icons are referenced by the id of an existing attachment. This API does not yet expose a way to upload attachments.
## Pagination
List endpoints return a page of results together with a `page` object. To fetch the next page, pass the returned `next_cursor` value back in the `cursor` query parameter.
## Errors
Errors are returned as RFC 9457 problem documents (`application/problem+json`) using the `ProblemDetail` schema.'
servers:
- url: https://api.joinblink.com/api/platform
description: Production API. Replace with the base URL for your environment.
security:
- bearerAuth: []
tags:
- name: Messages
description: Send, read, edit and delete messages within a chat.
paths:
/chats/{chatId}/messages:
get:
tags:
- Messages
summary: List messages from a chat
operationId: listMessages
description: 'Returns a page of messages from the given chat, ordered from newest to oldest. Pages backwards through history: pass the returned page''s `next_cursor` back via the `cursor` query parameter to fetch the messages sent before the last one on this page.'
parameters:
- $ref: '#/components/parameters/ChatId'
- $ref: '#/components/parameters/Size'
- $ref: '#/components/parameters/Cursor'
responses:
'200':
description: A page of messages, newest first.
content:
application/json:
schema:
$ref: '#/components/schemas/CursorPageMessage'
'400':
$ref: '#/components/responses/BadRequest'
'401':
$ref: '#/components/responses/Unauthorized'
'403':
$ref: '#/components/responses/Forbidden'
'404':
$ref: '#/components/responses/NotFound'
'422':
$ref: '#/components/responses/UnprocessableEntity'
post:
tags:
- Messages
summary: Send a new message into a chat
operationId: sendMessage
description: Sends a new message into the given chat, and returns the created message in full, exactly as a subsequent GET of the message would. The sender is required and must be the authenticated app making the request; posting under an alias or on behalf of another user or app is not permitted. The body carries the structured body and any attached files.
parameters:
- $ref: '#/components/parameters/ChatId'
requestBody:
required: true
content:
application/json:
schema:
$ref: '#/components/schemas/SendMessage'
examples:
markdown:
summary: Markdown message from an app, with link unfurling
value:
sender:
'@type': app
app_identity_id: aid-00000000-0000-0000-0000-000000000005
body:
'@type': markdown
markdown: '**Heads up:** the build is broken — see #123.'
unfurl_links: true
with_attachment:
summary: Message with an image attachment
value:
sender:
'@type': app
app_identity_id: aid-00000000-0000-0000-0000-000000000005
files:
- attachment_id: a-00000000-0000-0000-0000-000000000000
type: IMAGE
caption: Office whiteboard photo
body:
'@type': markdown
markdown: Notes from today's standup
responses:
'201':
description: The created message.
content:
application/json:
schema:
$ref: '#/components/schemas/Message'
'400':
$ref: '#/components/responses/BadRequest'
'401':
$ref: '#/components/responses/Unauthorized'
'403':
$ref: '#/components/responses/Forbidden'
'404':
$ref: '#/components/responses/NotFound'
'422':
$ref: '#/components/responses/UnprocessableEntity'
/chats/{chatId}/messages/{messageId}:
get:
tags:
- Messages
summary: Look up a single message
operationId: getMessage
description: Looks up a single message by its identifier and returns it in full.
parameters:
- $ref: '#/components/parameters/ChatId'
- $ref: '#/components/parameters/MessageId'
responses:
'200':
description: The message.
content:
application/json:
schema:
$ref: '#/components/schemas/Message'
'401':
$ref: '#/components/responses/Unauthorized'
'403':
$ref: '#/components/responses/Forbidden'
'404':
$ref: '#/components/responses/NotFound'
'422':
$ref: '#/components/responses/UnprocessableEntity'
patch:
tags:
- Messages
summary: Edit the contents of a message
operationId: updateMessage
description: 'Edits the contents of an existing message, and returns the edited message in full, exactly as a subsequent GET of the message would, carrying the server-set `edited_at`. Each field follows PATCH semantics: omit a field to leave it unchanged, or supply a value to replace it. An empty `files` list removes all attachments.'
parameters:
- $ref: '#/components/parameters/ChatId'
- $ref: '#/components/parameters/MessageId'
requestBody:
required: true
content:
application/json:
schema:
$ref: '#/components/schemas/EditMessage'
examples:
editBody:
summary: Replace the message body
value:
body:
'@type': markdown
markdown: '**Update:** the build is green again.'
responses:
'200':
description: The edited message.
content:
application/json:
schema:
$ref: '#/components/schemas/Message'
'400':
$ref: '#/components/responses/BadRequest'
'401':
$ref: '#/components/responses/Unauthorized'
'403':
$ref: '#/components/responses/Forbidden'
'404':
$ref: '#/components/responses/NotFound'
'422':
$ref: '#/components/responses/UnprocessableEntity'
delete:
tags:
- Messages
summary: Delete a message
operationId: deleteMessage
description: 'Deletes an existing message by clearing it: the message is left in place, but its attachments are discarded and its body is replaced with a `deleted` marker, so clients can indicate that a message used to exist at this position. The deleted message is returned in full, exactly as a subsequent GET of it would with a `deleted` body and no files.'
parameters:
- $ref: '#/components/parameters/ChatId'
- $ref: '#/components/parameters/MessageId'
responses:
'200':
description: The deleted message.
content:
application/json:
schema:
$ref: '#/components/schemas/Message'
example:
message_id:
chat_id: c-00000000-0000-0000-0000-000000000000
local_message_id: m-00000000-0000-0000-0000-000000000000
sender:
'@type': app
app_identity_id: aid-00000000-0000-0000-0000-000000000000
created_at: '2026-09-04T18:08:03.446993Z'
edited_at: '2026-09-08T08:07:40.798289Z'
files: []
body:
'@type': deleted
reactions: []
'401':
$ref: '#/components/responses/Unauthorized'
'403':
$ref: '#/components/responses/Forbidden'
'404':
$ref: '#/components/responses/NotFound'
'422':
$ref: '#/components/responses/UnprocessableEntity'
/chats/{chatId}/messages/{messageId}/permalink:
get:
tags:
- Messages
summary: Get a durable link to a message
operationId: getMessagePermalink
description: Returns a durable link to a message, suitable for referencing or sharing the message outside the normal chat flow. Works for messages sent by both users and apps.
parameters:
- $ref: '#/components/parameters/ChatId'
- $ref: '#/components/parameters/MessageId'
responses:
'200':
description: The message permalink.
content:
application/json:
schema:
$ref: '#/components/schemas/MessagePermalink'
'401':
$ref: '#/components/responses/Unauthorized'
'403':
$ref: '#/components/responses/Forbidden'
'404':
$ref: '#/components/responses/NotFound'
'422':
$ref: '#/components/responses/UnprocessableEntity'
components:
schemas:
App:
type: object
description: A message sent by an automated app.
required:
- '@type'
properties:
'@type':
type: string
enum:
- app
example: app
app_identity_id:
type: string
description: The app that sent the message.
example: aid-00000000-0000-0000-0000-000000000000
Sender:
description: The originator of a message. A message read back may have been sent by a user, by a user acting under an alias, by an app, or by the system itself (for membership changes, chat lifecycle events, etc.). Serialised with an `@type` discriminator. When sending a message only the authenticated app may be named as the sender — see `SendMessage`.
oneOf:
- $ref: '#/components/schemas/User'
- $ref: '#/components/schemas/Alias'
- $ref: '#/components/schemas/App'
- $ref: '#/components/schemas/System'
discriminator:
propertyName: '@type'
mapping:
user: '#/components/schemas/User'
alias: '#/components/schemas/Alias'
app: '#/components/schemas/App'
system: '#/components/schemas/System'
Reaction:
type: object
description: A reaction recorded against a message. `users` always contains the authenticated user if they reacted, but might not contain every user who reacted; `count` is always the total number of unique users who recorded the reaction (so it may exceed the length of `users`).
properties:
reaction:
type: string
description: The reaction, as an emoji string.
example: 👍
count:
type: integer
format: int64
description: The number of unique users who have recorded this reaction.
example: 3
users:
type: array
description: The IDs of a possible subset of users who have recorded this reaction; always includes the authenticated user if they recorded it.
uniqueItems: true
items:
type: string
example: u-00000000-0000-0000-0000-000000000000
Header:
type: object
description: 'A header body: the automatically-generated first message of a chat, announcing its creation (e.g. "Alex created the chat"). Attributed to whoever actually created the chat (a user or app sender, never system). Response-only: created by the system when a chat is created and never sent or edited by a client.'
required:
- '@type'
properties:
'@type':
type: string
enum:
- header
example: header
text:
type: string
description: A human-readable rendering of the chat-creation notice.
example: Alex created the chat.
SendMessage:
type: object
description: Parameters for sending a new message into a chat.
required:
- sender
properties:
sender:
allOf:
- $ref: '#/components/schemas/App'
description: The message sender. Required, and must be the authenticated app making the request — an `app` sender carrying your own app identity. Posting under an alias or on behalf of another user or app is not permitted.
files:
type: array
description: Attachments to include with the message.
items:
$ref: '#/components/schemas/File'
body:
$ref: '#/components/schemas/Body'
unfurl_links:
type: boolean
description: Whether links found in the message should be unfurled into previews.
example: true
User:
type: object
description: A message sent by a regular user, posting under their own identity.
required:
- '@type'
properties:
'@type':
type: string
enum:
- user
example: user
user_id:
type: string
description: The user who sent the message.
example: u-00000000-0000-0000-0000-000000000000
Alias:
type: object
description: A message sent by a user posting under an alias.
required:
- '@type'
properties:
'@type':
type: string
enum:
- alias
example: alias
user_id:
type: string
description: The underlying user who sent the message.
example: u-00000000-0000-0000-0000-000000000000
alias_id:
type: string
description: The alias the user was posting as.
example: al-00000000-0000-0000-0000-000000000000
ProblemDetail:
type: object
additionalProperties: true
description: An RFC 9457 problem document describing why the request failed.
properties:
type:
type: string
format: uri
description: Identifies the problem type; `about:blank` when unclassified.
example: about:blank
title:
type: string
description: Short, human-readable summary of the problem type.
example: Not Found
status:
type: integer
format: int32
description: The HTTP status code, repeated in the body.
example: 404
detail:
type: string
description: Human-readable explanation specific to this occurrence.
example: Not Found
instance:
type: string
format: uri
description: The path of the request that failed.
File:
type: object
description: A file attached to a message.
properties:
attachment_id:
type: string
description: The id of an existing attachment in the attachments service. This API does not yet provide a way to upload attachments.
example: a-00000000-0000-0000-0000-000000000000
type:
type: string
description: Broad category describing the content of an attached file. Determines how clients should preview or render the attachment.
enum:
- UNKNOWN
- IMAGE
- AUDIO
- VIDEO
caption:
type: string
description: Optional caption describing the file. Used as alt-text for items being visually rendered.
example: Office whiteboard photo
Empty:
type: object
description: An empty body, used for messages that carry no renderable content of their own (for example, messages whose payload is conveyed entirely through attachments).
required:
- '@type'
properties:
'@type':
type: string
enum:
- empty
example: empty
Structured:
type: object
description: 'A structured-message body: a placeholder for rich, structured messages whose concrete shape is not yet defined. Response-only for now — a message may not be sent or edited with this body type; the variant exists so pre-existing rich messages can be represented when read back.'
required:
- '@type'
properties:
'@type':
type: string
enum:
- structured
example: structured
Body:
description: The structured body of a message. Always has a discriminated content type indicating how clients should render it. Serialised with an `@type` discriminator. On send and edit only `markdown` and `empty` may be supplied; the remaining variants are response-only.
oneOf:
- $ref: '#/components/schemas/Markdown'
- $ref: '#/components/schemas/Empty'
- $ref: '#/components/schemas/Structured'
- $ref: '#/components/schemas/SystemBody'
- $ref: '#/components/schemas/Header'
- $ref: '#/components/schemas/Deleted'
- $ref: '#/components/schemas/Unknown'
discriminator:
propertyName: '@type'
mapping:
markdown: '#/components/schemas/Markdown'
empty: '#/components/schemas/Empty'
structured: '#/components/schemas/Structured'
system: '#/components/schemas/SystemBody'
header: '#/components/schemas/Header'
deleted: '#/components/schemas/Deleted'
unknown: '#/components/schemas/Unknown'
PageMetadata:
type: object
description: Metadata describing a page of a cursor-paginated listing.
properties:
size:
type: integer
format: int64
description: The number of items in this page.
total_elements:
type:
- integer
- 'null'
format: int64
description: Total number of items across all pages, when known; otherwise null.
total_pages:
type:
- integer
- 'null'
format: int64
description: Total number of pages, when known; otherwise null.
has_next:
type: boolean
description: Whether a further page is available.
next_cursor:
type:
- string
- 'null'
description: Opaque, base64-encoded cursor for the next page; null if there is none.
prev_cursor:
type:
- string
- 'null'
description: Opaque, base64-encoded cursor for the previous page; null if there is none.
Markdown:
type: object
description: A Markdown body, expected to be rendered by a Markdown-capable client.
required:
- '@type'
properties:
'@type':
type: string
enum:
- markdown
example: markdown
markdown:
type: string
description: The Markdown source for the message.
example: '**Heads up:** the build is broken — see #123.'
System:
type: object
description: A message generated by the chat system itself, rather than by any user or app. Used for system notices such as membership changes or chat lifecycle events.
required:
- '@type'
properties:
'@type':
type: string
enum:
- system
example: system
CursorPageMessage:
type: object
description: A page of messages.
properties:
content:
type: array
items:
$ref: '#/components/schemas/Message'
page:
$ref: '#/components/schemas/PageMetadata'
EditMessage:
type: object
description: 'Parameters for editing an existing message. Each field follows PATCH semantics: omit a field to leave it unchanged, or supply a value to replace it. An empty `files` list removes all attachments.'
properties:
files:
type: array
description: If present, the new set of attached files; an empty list removes all attachments.
items:
$ref: '#/components/schemas/File'
body:
$ref: '#/components/schemas/Body'
MessageId:
type: object
description: Globally unique identifier for a message, composed of the owning chat id and the local message id that distinguishes the message within that chat.
required:
- chat_id
- local_message_id
properties:
chat_id:
type: string
description: Globally unique identifier for a chat; a `c-` prefixed string.
example: c-00000000-0000-0000-0000-000000000000
local_message_id:
type: string
description: Identifies a message within its enclosing chat; an `m-` prefixed string. Only meaningful in combination with a chat id.
example: m-00000000-0000-0000-0000-000000000000
MessagePermalink:
type: object
description: A durable link to a message.
properties:
permalink:
type: string
description: The durable URL pointing directly at the message.
example: https://app.joinblink.com/#/inbox/c-00000000-0000-0000-0000-000000000000#m-00000000-0000-0000-0000-000000000000
Unknown:
type: object
description: 'A body for a pre-existing message that cannot be represented by any other variant. Response-only: it appears when messages are read back so a chat''s history can always be listed, and is never accepted on the way in. It carries no payload, so clients should render it as a placeholder.'
required:
- '@type'
properties:
'@type':
type: string
enum:
- unknown
example: unknown
Deleted:
type: object
description: A tombstone body left behind when a message is soft-deleted. Indicates to clients that a message used to be present at this position but has since been removed; any prior content and attachments are discarded.
required:
- '@type'
properties:
'@type':
type: string
enum:
- deleted
example: deleted
Message:
type: object
description: A single message sent within a Blink chat.
properties:
message_id:
$ref: '#/components/schemas/MessageId'
sender:
$ref: '#/components/schemas/Sender'
created_at:
type: string
format: date-time
description: The instant the message was originally sent.
example: '2026-05-14T09:30:00Z'
edited_at:
type: string
format: date-time
description: The instant the message's content was last edited; absent if it has never been edited. Changes to related structures such as reactions do not update this value.
example: '2026-05-14T09:32:11Z'
files:
type: array
description: Attachments that accompany this message.
items:
$ref: '#/components/schemas/File'
body:
$ref: '#/components/schemas/Body'
reactions:
type: array
description: Reactions recorded against this message. Read-only in this API.
items:
$ref: '#/components/schemas/Reaction'
SystemBody:
type: object
description: 'A system-generated body, used for messages emitted by the chat system itself (membership changes, chat lifecycle events, etc.). Response-only: it is paired one-to-one with the `system` sender and cannot be sent or edited by a client.'
required:
- '@type'
properties:
'@type':
type: string
enum:
- system
example: system
text:
type: string
description: A human-readable rendering of the system notice.
example: Alex joined the chat.
responses:
Forbidden:
description: The caller is not permitted to perform this action.
content:
application/problem+json:
schema:
$ref: '#/components/schemas/ProblemDetail'
Unauthorized:
description: Authentication is missing or invalid.
content:
application/problem+json:
schema:
$ref: '#/components/schemas/ProblemDetail'
UnprocessableEntity:
description: The request was well-formed but failed validation.
content:
application/problem+json:
schema:
$ref: '#/components/schemas/ProblemDetail'
NotFound:
description: The requested resource does not exist.
content:
application/problem+json:
schema:
$ref: '#/components/schemas/ProblemDetail'
BadRequest:
description: The request body or a parameter could not be read.
content:
application/problem+json:
schema:
$ref: '#/components/schemas/ProblemDetail'
parameters:
MessageId:
name: messageId
in: path
required: true
description: Identifies a message within its enclosing chat; an `m-` prefixed string. Only meaningful in combination with a chat id.
schema:
type: string
example: m-00000000-0000-0000-0000-000000000000
ChatId:
name: chatId
in: path
required: true
description: Globally unique identifier for a chat; a `c-` prefixed string.
schema:
type: string
example: c-00000000-0000-0000-0000-000000000000
Cursor:
name: cursor
in: query
required: false
description: Pagination cursor token. Pass the `next_cursor` from a previous page to fetch the next one.
schema:
type: string
Size:
name: size
in: query
required: false
description: The number of items to return per page, between 1 and 150.
schema:
type: integer
format: int32
default: 50
minimum: 1
maximum: 150
securitySchemes:
bearerAuth:
type: http
scheme: bearer
description: 'A bearer token supplied in the `Authorization` header as `Authorization: Bearer <token>`.'
x-provenance:
method: searched
source: https://developer.joinblink.com/reference
harvested: '2026-10-28'
tool: harvest-readme-openapi.py
note: Assembled verbatim from the OpenAPI definition ReadMe embeds in each operation page of the provider's developer portal; paths and components merged by API title, nothing authored.
assembled_from:
- https://developer.joinblink.com/reference/createchat.md
- https://developer.joinblink.com/reference/deletechat.md
- https://developer.joinblink.com/reference/deletemessage.md
- https://developer.joinblink.com/reference/getchat.md
- https://developer.joinblink.com/reference/getmessage.md
- https://developer.joinblink.com/reference/getmessagepermalink.md
- https://developer.joinblink.com/reference/getmymembership.md
- https://developer.joinblink.com/reference/grantaccess.md
- https://developer.joinblink.com/reference/joinchat.md
- https://developer.joinblink.com/reference/leavechat.md
- https://developer.joinblink.com/reference/listchatinbox.md
- https://developer.joinblink.com/reference/listgrants.md
- https://developer.joinblink.com/reference/listmembers.md
- https://developer.joinblink.com/reference/listmessages.md
- https://developer.joinblink.com/reference/removeappmember.md
- https://developer.joinblink.com/reference/removeusermember.md
- https://developer.joinblink.com/reference/revokeappaccess.md
- https://developer.joinblink.com/reference/revokeuseraccess.md
- https://developer.joinblink.com/reference/sendmessage.md
- https://developer.joinblink.com/reference/updateappmemberrole.md
- https://developer.joinblink.com/reference/updatechat.md
- https://developer.joinblink.com/reference/updatemessage.md
- https://developer.joinblink.com/reference/updateusermemberrole.md
merge:
pages: 23
deduped: 380
conflicts_kept_first: 0