ReasonBlocks

ReasonBlocks is a Y Combinator (Spring 2026) startup building a drop-in runtime layer that makes production AI agents observable, self-correcting, and cheaper to run. The platform detects failing agent trajectories (loops and redundant work), compresses stale tool outputs and message histories to cut token spend, and builds a private learning library of reasoning patterns (E-traces) that steer future runs. It ships as a Python SDK with first-party integrations for LangChain, LangGraph, the OpenAI Agents SDK, and the Anthropic Claude / Claude Agent SDK, plus a language-agnostic REST API (rb-api) so any custom agent harness can wire in over three HTTP calls. Reported results include a 42% accuracy gain and ~52% token reduction on SWE-bench Pro.

ReasonBlocks publishes 9 APIs on the APIs.io network, including Billing API, Codebase Findings API, Health API, and 6 more. Tagged areas include Company, AI Agents, Agent Observability, LLM, and Developer Tools.

ReasonBlocks’ developer surface includes documentation, API reference, getting-started guide, authentication, sandbox, and 17 more developer resources.

🌐 Visit website 📡 Source on GitHub

35.5/100 thin ▬ flat Agent 24/100 agent aware Full breakdown ↓
scored 2026-09-08 · rubric v0.20.0

1 APIs

Company AI AgentsAgent ObservabilityLLM Developer ToolsToken OptimizationAgent SteeringMachine-Learning Artificial Intelligence SDK

Kin Score

Kin Score How this is scored →
scored 2026-09-08 · rubric v0.20.0

Composite quality — 35.5/100 · thin

Contract Quality 12.2 / 23

Developer Ergonomics 11.9 / 18

Access Clarity 0.0 / 18

Operational Transparency 1.2 / 12

Contract Governance 0.5 / 11

Discoverability 6.8 / 9

Create-or-Update Ergonomics 0.0 / 10

Agent readiness — 24/100 · agent aware

Machine-Readable Contract 18 / 18

Agentic Access Contract 10 / 10

Documented Reversibility 0 / 6

MCP Server 0 / 12

Machine-Readable Auth 10 / 10

Idempotency 0 / 9

Stable Error Semantics 8 / 8

Request/Response Examples 0 / 7

Rate-Limit Signaling 0 / 7

Typed Event Surface 0 / 6

Agent Skills 5 / 5

Well-Known Catalog 0 / 4

Consent & Bot Identity 0 / 3

A2A Agent Card 0 / 8

Dry-Run / Simulate Mode 0 / 4

Delegated User Identity 0 / 6

Protected Resource Metadata 0 / 5

Registration Without a Human 0 / 6

Agentic Commerce Well-Known Document 0 / 5

Create-or-Update Ergonomics applies to this provider. This API accepts writes, so it carries 10 points of the composite. It is scored from the published contracts themselves: whether a caller can create-or-update in one call, whether the write accepts a key the caller already holds, and whether the response says which branch ran. Without that, every write needs a search-and-branch in front of it, and the first time that check is skipped a duplicate record is created. Scored against the observed mean rather than raw — a provider at the catalog average is unchanged by this facet, not penalised by it.

Improve this rating by publishing the missing artifacts — every area above can be raised, and the full rubric is at apis.io/rating/. Every facet and dimension name above is a link: it opens that measurement's own page — what it means, the exact checks that feed it, how the whole catalog distributes on it, and the providers at the top of it. This rating is computed from github.com/api-evangelist/reasonblocks: open an issue to ask a question, or submit a pull request to add artifacts. Submit an artifact on GitHub — free → Manage your own listing — the Influence plan, $499/mo →

APIs 9

Individual APIs this provider publishes, each with its own machine-readable definition.

ReasonBlocks Billing API

The Billing API from ReasonBlocks — 1 operation(s) for billing.

ReasonBlocks Codebase Findings API

The Codebase Findings API from ReasonBlocks — 5 operation(s) for codebase findings.

ReasonBlocks Health API

The Health API from ReasonBlocks — 1 operation(s) for health.

ReasonBlocks monitor API

The monitor API from ReasonBlocks — 11 operation(s) for monitor.

ReasonBlocks Monitor Telemetry API

The Monitor Telemetry API from ReasonBlocks — 11 operation(s) for monitor telemetry.

ReasonBlocks Monitors API

The Monitors API from ReasonBlocks — 1 operation(s) for monitors.

ReasonBlocks Pattern Library API

The Pattern Library API from ReasonBlocks — 2 operation(s) for pattern library.

ReasonBlocks Patterns & Traces API

The Patterns & Traces API from ReasonBlocks — 2 operation(s) for patterns & traces.

ReasonBlocks Scoring API

The Scoring API from ReasonBlocks — 1 operation(s) for scoring.

Scroll for all 9

Open Collections 10

Open, tool-agnostic API collections (OpenAPI-derived and Bruno).

API Collection

OPEN COLLECTION

ReasonBlocks Billing API

OPEN COLLECTION

ReasonBlocks Billing Codebase Findings API

OPEN COLLECTION

ReasonBlocks Billing Health API

OPEN COLLECTION

ReasonBlocks Billing monitor API

OPEN COLLECTION

ReasonBlocks Billing Monitor Telemetry API

OPEN COLLECTION

ReasonBlocks Billing Monitors API

OPEN COLLECTION

ReasonBlocks Billing Pattern Library API

OPEN COLLECTION

ReasonBlocks Billing Patterns & Traces API

OPEN COLLECTION

ReasonBlocks Billing Scoring API

OPEN COLLECTION

Scroll for all 10

Security Posture 2

Authentication, domain security, vulnerability disclosure, and trust-center signals.

Reasonblocks Authentication

http · 1 scheme

SECURITY

Reasonblocks Domain Security

TLSv1.3 · HSTS · DNSSEC · DMARC

SECURITY

Agentic Access 1

Recommended x-agentic-access execution contracts for AI agents.

Reasonblocks Agentic Access

32 operations · 18 acting

AGENTIC

Resources

Get Started 3

Portal, sign-up, and the first successful call

DeveloperPortal

DeveloperPortal

GettingStarted

GettingStarted

Sandbox

Sandbox

Documentation 2

Reference material describing how the API behaves

Documentation

Documentation

APIReference

APIReference

Agent Surfaces 4

MCP servers, agent skills, and machine-readable catalogs

LLMsTxt

LLMsTxt

X-MCPServerCandidate

X-MCPServerCandidate

AgenticAccess

AgenticAccess

AgentSkill

AgentSkill

Design & Contract 5

Pagination, idempotency, versioning, errors, and events

Conformance

ErrorCatalog

Lifecycle

Conventions

DataModel

Build 3

SDKs, sample code, and the tooling you integrate with

GitHubOrganization

GitHubOrganization

Packages

Packages

SDKs

SDKs

Access & Security 2

Authentication, authorization, and security posture

Authentication

Authentication

DomainSecurity

DomainSecurity

Operate 1

Status, limits, changes, and where to get help

Deprecation

Deprecation

Company 1

The organization behind the API

Website

Website

Other 1

Properties that don't map to a standard resource type

Overlay

Overlay

Source (apis.yml)

aid: reasonblocks
name: ReasonBlocks
description: ReasonBlocks is a Y Combinator (Spring 2026) startup building a drop-in runtime layer that makes production AI
  agents observable, self-correcting, and cheaper to run. The platform detects failing agent trajectories (loops and redundant
  work), compresses stale tool outputs and message histories to cut token spend, and builds a private learning library of
  reasoning patterns (E-traces) that steer future runs. It ships as a Python SDK with first-party integrations for LangChain,
  LangGraph, the OpenAI Agents SDK, and the Anthropic Claude / Claude Agent SDK, plus a language-agnostic REST API (rb-api)
  so any custom agent harness can wire in over three HTTP calls. Reported results include a 42% accuracy gain and ~52% token
  reduction on SWE-bench Pro.
url: https://raw.githubusercontent.com/api-evangelist/reasonblocks/refs/heads/main/apis.yml
x-type: company
x-source: vc-portfolio
x-backed-by:
- y-combinator
x-tier: profiled
x-tier-reason: portfolio-lead-enriched
deliveryModel:
  model: unknown
  open_source: false
  commercial: false
  callable_host: true
  label: Delivery model not determined — needs a product licence on record
  confidence: low
  source:
  - openapi
  generated: '2026-08-28'
  method: derived
accessModel:
  pricing: unknown
  onboarding: unknown
  trial: false
  try_now: false
  public: false
  label: Unknown
  confidence: low
  source:
  - authentication
  - security
  - sandbox
  generated: '2026-09-03'
  method: derived
image: https://reasonblocks.com/rb.png
specificationVersion: '0.23'
created: '2026-07-17'
modified: '2026-07-21'
tags:
- Company
- AI Agents
- Agent Observability
- LLM
- Developer Tools
- Token Optimization
- Agent Steering
- Machine-Learning
- Artificial Intelligence
- SDK
tags_raw:
- Company
- AI Agents
- Agent Observability
- LLM
- Developer Tools
- Token Optimization
- Agent Steering
- Machine Learning
- Artificial Intelligence
- SDK
apis:
- aid: reasonblocks:reasonblocks-billing-api
  name: ReasonBlocks Billing API
  description: The Billing API from ReasonBlocks — 1 operation(s) for billing.
  humanURL: https://docs.reasonblocks.com/api-reference/rest-api/overview
  baseURL: https://rb-api.reasonblocks.com
  tags:
  - Billing
  properties:
  - type: OpenAPI
    url: openapi/reasonblocks-billing-api-openapi.yml
  - type: Documentation
    url: https://docs.reasonblocks.com/introduction
  - type: APIReference
    url: https://rb-api.reasonblocks.com/docs
  - type: GettingStarted
    url: https://docs.reasonblocks.com/quickstart
- aid: reasonblocks:reasonblocks-codebase-findings-api
  name: ReasonBlocks Codebase Findings API
  description: The Codebase Findings API from ReasonBlocks — 5 operation(s) for codebase findings.
  humanURL: https://docs.reasonblocks.com/api-reference/rest-api/overview
  baseURL: https://rb-api.reasonblocks.com
  tags:
  - Codebase Findings
  properties:
  - type: OpenAPI
    url: openapi/reasonblocks-codebase-findings-api-openapi.yml
  - type: Documentation
    url: https://docs.reasonblocks.com/introduction
  - type: APIReference
    url: https://rb-api.reasonblocks.com/docs
  - type: GettingStarted
    url: https://docs.reasonblocks.com/quickstart
- aid: reasonblocks:reasonblocks-health-api
  name: ReasonBlocks Health API
  description: The Health API from ReasonBlocks — 1 operation(s) for health.
  humanURL: https://docs.reasonblocks.com/api-reference/rest-api/overview
  baseURL: https://rb-api.reasonblocks.com
  tags:
  - Health
  properties:
  - type: OpenAPI
    url: openapi/reasonblocks-health-api-openapi.yml
  - type: Documentation
    url: https://docs.reasonblocks.com/introduction
  - type: APIReference
    url: https://rb-api.reasonblocks.com/docs
  - type: GettingStarted
    url: https://docs.reasonblocks.com/quickstart
- aid: reasonblocks:reasonblocks-monitor-api
  name: ReasonBlocks monitor API
  description: The monitor API from ReasonBlocks — 11 operation(s) for monitor.
  humanURL: https://docs.reasonblocks.com/api-reference/rest-api/overview
  baseURL: https://rb-api.reasonblocks.com
  tags:
  - Monitors
  tags_raw:
  - monitor
  properties:
  - type: OpenAPI
    url: openapi/reasonblocks-monitor-api-openapi.yml
  - type: Documentation
    url: https://docs.reasonblocks.com/introduction
  - type: APIReference
    url: https://rb-api.reasonblocks.com/docs
  - type: GettingStarted
    url: https://docs.reasonblocks.com/quickstart
- aid: reasonblocks:reasonblocks-monitor-telemetry-api
  name: ReasonBlocks Monitor Telemetry API
  description: The Monitor Telemetry API from ReasonBlocks — 11 operation(s) for monitor telemetry.
  humanURL: https://docs.reasonblocks.com/api-reference/rest-api/overview
  baseURL: https://rb-api.reasonblocks.com
  tags:
  - Monitor Telemetry
  properties:
  - type: OpenAPI
    url: openapi/reasonblocks-monitor-telemetry-api-openapi.yml
  - type: Documentation
    url: https://docs.reasonblocks.com/introduction
  - type: APIReference
    url: https://rb-api.reasonblocks.com/docs
  - type: GettingStarted
    url: https://docs.reasonblocks.com/quickstart
- aid: reasonblocks:reasonblocks-monitors-api
  name: ReasonBlocks Monitors API
  description: The Monitors API from ReasonBlocks — 1 operation(s) for monitors.
  humanURL: https://docs.reasonblocks.com/api-reference/rest-api/overview
  baseURL: https://rb-api.reasonblocks.com
  tags:
  - Monitors
  properties:
  - type: OpenAPI
    url: openapi/reasonblocks-monitors-api-openapi.yml
  - type: Documentation
    url: https://docs.reasonblocks.com/introduction
  - type: APIReference
    url: https://rb-api.reasonblocks.com/docs
  - type: GettingStarted
    url: https://docs.reasonblocks.com/quickstart
- aid: reasonblocks:reasonblocks-pattern-library-api
  name: ReasonBlocks Pattern Library API
  description: The Pattern Library API from ReasonBlocks — 2 operation(s) for pattern library.
  humanURL: https://docs.reasonblocks.com/api-reference/rest-api/overview
  baseURL: https://rb-api.reasonblocks.com
  tags:
  - Pattern Library
  properties:
  - type: OpenAPI
    url: openapi/reasonblocks-pattern-library-api-openapi.yml
  - type: Documentation
    url: https://docs.reasonblocks.com/introduction
  - type: APIReference
    url: https://rb-api.reasonblocks.com/docs
  - type: GettingStarted
    url: https://docs.reasonblocks.com/quickstart
- aid: reasonblocks:reasonblocks-patterns-traces-api
  name: ReasonBlocks Patterns & Traces API
  description: The Patterns & Traces API from ReasonBlocks — 2 operation(s) for patterns & traces.
  humanURL: https://docs.reasonblocks.com/api-reference/rest-api/overview
  baseURL: https://rb-api.reasonblocks.com
  tags:
  - Patterns & Traces
  properties:
  - type: OpenAPI
    url: openapi/reasonblocks-patterns-traces-api-openapi.yml
  - type: Documentation
    url: https://docs.reasonblocks.com/introduction
  - type: APIReference
    url: https://rb-api.reasonblocks.com/docs
  - type: GettingStarted
    url: https://docs.reasonblocks.com/quickstart
- aid: reasonblocks:reasonblocks-scoring-api
  name: ReasonBlocks Scoring API
  description: The Scoring API from ReasonBlocks — 1 operation(s) for scoring.
  humanURL: https://docs.reasonblocks.com/api-reference/rest-api/overview
  baseURL: https://rb-api.reasonblocks.com
  tags:
  - Scoring
  properties:
  - type: OpenAPI
    url: openapi/reasonblocks-scoring-api-openapi.yml
  - type: Documentation
    url: https://docs.reasonblocks.com/introduction
  - type: APIReference
    url: https://rb-api.reasonblocks.com/docs
  - type: GettingStarted
    url: https://docs.reasonblocks.com/quickstart
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com
- FN: APIs.json
  email: info@apis.io
common:
- type: DeveloperPortal
  url: https://docs.reasonblocks.com/
- type: Documentation
  url: https://docs.reasonblocks.com/introduction
- type: APIReference
  url: https://rb-api.reasonblocks.com/docs
- type: GettingStarted
  url: https://docs.reasonblocks.com/quickstart
- type: GitHubOrganization
  url: https://github.com/ReasonBlocks
- type: Website
  url: https://reasonblocks.com
- type: Authentication
  url: authentication/reasonblocks-authentication.yml
- type: Packages
  url: packages/reasonblocks-packages.yml
- type: SDKs
  url: packages/reasonblocks-packages.yml
- type: LLMsTxt
  url: llms/reasonblocks-llms.txt
- type: X-MCPServerCandidate
  url: mcp/reasonblocks-mcp.yml
  note: 'Renamed from MCPServer 2026-09-03 (roadmap#247): the manifest self-describes as status: candidate — a tool list derived
    from the published API contracts, not an existing server. The scorer already read the manifest and reported mcp_server
    correctly; the MCPServer type was crediting the artifact-type surfaces with a server that does not exist.'
- type: Overlay
  url: overlays/reasonblocks-openapi-overlay.yaml
- type: Conformance
  url: conformance/reasonblocks-conformance.yml
- type: ErrorCatalog
  url: errors/reasonblocks-problem-types.yml
- type: Lifecycle
  url: lifecycle/reasonblocks-lifecycle.yml
- type: Deprecation
  url: https://docs.reasonblocks.com/api-reference/rest-api/versioning
- type: Conventions
  url: conventions/reasonblocks-conventions.yml
- type: DataModel
  url: data-model/reasonblocks-data-model.yml
- type: Sandbox
  url: sandbox/reasonblocks-sandbox.yml
- type: DomainSecurity
  url: security/reasonblocks-domain-security.yml
- type: AgenticAccess
  url: agentic-access/reasonblocks-agentic-access.yml
- type: AgentSkill
  url: skills/_index.yml
x-enrichment:
  date: '2026-07-21'
  status: enriched
  artifacts_added: 18
  pass: local-v1

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