Library of Congress
The Library of Congress is the largest library in the world and the research arm of the US Congress. It provides REST APIs for accessing digitized collections, Congress.gov legislative data, bibliographic records, historic newspapers via Chronicling America, maps, photographs, manuscripts, and historical government documents. The loc.gov JSON API requires no authentication, while the Congress.gov API requires a free API key.
Real signal across most facets with visible, nameable gaps — the contract exists but is thin, or the portal is good while governance and commercial terms are absent.
API Evangelist profiles Library of Congress the way a machine reads it — 36 machine-readable artifacts across 25 APIs, pulled from the provider's own public surface and indexed so a developer, an analyst, or an AI agent can evaluate it against every other provider on the network.
Every provider in the network is reduced to the same set of machine-readable artifacts — OpenAPI contracts, event specifications, GraphQL schemas, runnable collections, pricing and rate-limit signals, security posture, OAuth scopes, and the agent surfaces (MCP servers and skills) that let software drive the API on its own. We profile them because the interface is the part of a company you can actually inspect: it is a truer signal of what a provider does than any marketing page. From those artifacts we compute the Kin Score — Library of Congress scores 51.8/100 (developing), with a separate agent-readiness read of 48/100 (agent ready). The full breakdown is below, followed by every artifact we hold — each card links through to its machine-readable definition on apis.io.
Kin Score
This is the API Evangelist rating — a single, repeatable read computed from the artifacts on this page. Green fill is points earned; the red track is points possible, so every bar shows earned-versus-possible at a glance.
Kin Score
How this is scored →scored 2026-07-27 · rubric v0.5
How we profile Library of Congress
Each block below is one kind of artifact we hold for Library of Congress. For each we say what it is and why it earns a place in the profile, then list every one we've indexed — capped at two rows, scroll within the panel for the rest.
APIs 25
Each API is captured as its own OpenAPI definition — every operation, parameter, and response. This is the single most useful machine-readable description of what an API does, and it's what lets us score, lint, mock, and generate against it without asking the provider for anything.
Individual APIs this provider publishes, each with its own machine-readable definition.
Chronicling America API
The Chronicling America API provides access to the historic American newspapers collection digitized by the Library of Congress and its partners. Endpoints allow searching and r...
Library of Congress amendments API
Returns amendment data from the API
Library of Congress bill API
Returns bill data from the API
Library of Congress bound-congressional-record API
Returns bound Congressional Record data from the API
Library of Congress collections API
Browse and access digital collections
Library of Congress committee API
Returns committee data from the API
Library of Congress committee-meeting API
Returns committee meeting data from the API
Library of Congress committee-print API
Returns committee print data from the API
Library of Congress committee-report API
Returns committee report data from the API
Library of Congress congress API
Returns congress and congressional sessions data from the API
Library of Congress congressional-record API
Returns Congressional Record data from the API
Library of Congress crsreport API
Returns Congressional Research Service (CRS) report data from the API
Library of Congress daily-congressional-record API
Returns daily Congressional Record data from the API
Library of Congress formats API
Browse items by format type
Library of Congress hearing API
Returns hearing data from the API
Library of Congress house-communication API
Returns House communication data from the API
Library of Congress house-requirement API
Returns House requirement data from the API
Library of Congress house-vote API
[BETA] Returns House of Representatives roll call vote data from the API
Library of Congress items API
Access individual item details
Library of Congress member API
Returns member data from the API
Library of Congress nomination API
Returns nomination data from the API
Library of Congress search API
Search across all loc.gov digital collections
Library of Congress senate-communication API
Returns Senate communication data from the API
Library of Congress summaries API
Returns summaries data from the API
Library of Congress treaty API
Returns treaty data from the API
Scroll within the panel for all 25 ·
Pricing Plans 1
Pricing is part of the interface. Machine-readable plans tell you what a tier costs and includes before you commit — one of the six things the Kin Score reads for commercial clarity.
Published pricing tiers and plan structures.
Loc Plans Pricing
PLANSRate Limits 1
Rate limits are the difference between a demo that works and a production integration that doesn't fall over. Publishing them is an operational-transparency signal — and a hard requirement for any agent that plans its own throughput.
Documented rate limits and quota policies.
Loc Rate Limits
RATE LIMITSFinOps 1
Cost, billing, and metering signals let a buyer model the financial operations of an API before it's live. We profile them for the same reason we profile pricing: the money is part of the contract.
Cost, billing, and metering signals for API financial operations.
Loc Finops
FINOPSSemantic Vocabularies 1
JSON-LD contexts give the data shared meaning across APIs. We profile them because semantics are what let a machine reconcile 'customer' here with 'customer' somewhere else.
JSON-LD contexts and semantic vocabularies used across these APIs.
Loc Context
JSON-LDSpectral Rules 1
Governance rulesets we run against this provider's specs — the automated checks behind parts of the score. Profiling them makes the quality bar explicit and re-runnable, not a matter of opinion.
Library of Congress API Rules
SPECTRALJSON Schema 1
Standalone JSON Schema definitions describe the data models behind the API. We profile them so the shapes are validatable on their own — useful long after a single request is forgotten.
Standalone JSON Schema definitions for this provider's data models.
Congress.gov API Schemas
JSON SCHEMAExamples 1
Real request and response payloads are what turn a spec from abstract into obvious — and they're one of the twelve things an agent needs to call an API correctly on the first try.
Example request and response payloads for these APIs.
Loc Congress Gov Examples
EXAMPLESecurity Posture 3
Authentication, domain security, vulnerability disclosure, and trust-center signals — the evidence that a provider takes security seriously enough to document it. We profile it because you can't govern what you can't see.
Authentication, domain security, vulnerability disclosure, and trust-center signals.
Agentic Access 1
An x-agentic-access contract marks which operations are safe for an agent to run on its own and which need a human in the loop. It is the difference between an API an agent can use and one it can use safely.
Recommended x-agentic-access execution contracts for AI agents.
Resources
Every other property we hold for Library of Congress — documentation, portals, status pages, policies, and corporate surface — grouped by the job it does, following the integrator's arc from getting started to running in production.
Documentation 1
Reference material describing how the API behaves
Agent Surfaces 1
MCP servers, agent skills, and machine-readable catalogs
Build 1
SDKs, sample code, and the tooling you integrate with
Access & Security 3
Authentication, authorization, and security posture
Operate 2
Status, limits, changes, and where to get help
Commercial 3
Pricing, plans, and the legal terms of use
Company 3
The organization behind the API
Other 1
Properties that don't map to a standard resource type
← All providers · Data indexed from github.com/api-evangelist/loc · machine-readable index on apis.io