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
38.9/100 thin ▬ flat Agent 65/100 agent native Full breakdown ↓
scored 2026-07-27 · rubric v0.5
AccessSelf serve
9 APIs 1 MCP Servers
CompanyAI AgentsAgent ObservabilityLLMDeveloper ToolsToken OptimizationAgent SteeringMachine LearningArtificial IntelligenceSDK

Kin Score

Kin Score Kin Score How this is scored →
scored 2026-07-27 · rubric v0.5
Composite quality — 38.9/100 · thin
Contract Quality 12.5 / 25
Developer Ergonomics 14.8 / 20
Commercial Clarity 0.0 / 20
Operational Transparency 1.7 / 13
Governance 0.0 / 12
Discoverability 10.0 / 10
Agent readiness — 65/100 · agent native
Machine-Readable Contract 18 / 18
Agentic Access Contract 15 / 15
MCP Server 12 / 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
Improve this rating by publishing the missing artifacts — every area above can be raised, and the full rubric is at apis.io/rating/. 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. Want it done for you? Prioritized profiling — $2,500 →

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

MCP Servers 1

Model Context Protocol servers that expose these APIs to AI agents.

reasonblocks-mcp.yml

MCP SERVER

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

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
 MCPServer
MCPServer
 AgenticAccess
AgenticAccess
 AgentSkill
AgentSkill

Design & Contract 5

Pagination, idempotency, versioning, errors, and events

Conformance
Conformance
 ErrorCatalog
ErrorCatalog
 Lifecycle
Lifecycle
 Conventions
Conventions
 DataModel
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)

apis.yml Raw ↑ 
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
accessModel:
  pricing: unknown
  onboarding: self-serve
  trial: false
  try_now: false
  public: false
  label: Self-serve signup
  confidence: medium
  source:
  - authentication
  generated: '2026-07-22'
  method: derived
image: https://reasonblocks.com/rb.png
specificationVersion: '0.20'
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
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:
  - 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: MCPServer
  url: mcp/reasonblocks-mcp.yml
- 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