Bazel is a fast, scalable, multi-language and extensible build tool open-sourced by Google. It supports software projects of any size across Java, C++, Go, Python, Rust, Swift, Kotlin, Scala, Android, iOS, and many other languages and platforms. Bazel uses a hermetic, sandboxed execution model with content-addressable caching, parallel builds, and remote execution. The project ships the `bazel` CLI, the Starlark extension language for build rules, the MODULE.bazel external-dependency system (Bzlmod), and the Bazel Central Registry — a public HTTP index registry that hosts community-maintained Bazel modules.
Bazel publishes 6 API contracts indexed on the APIs.io network, including Modules API, Registry API, and 4 more. Tagged areas include Build Systems, Build Tools, Bzlmod, CI/CD, and Developer Tools.
The Bazel catalog on APIs.io includes 1 JSON-LD context and 2 Spectral governance rulesets.
Bazel’s developer surface includes developer portal, documentation, getting-started guide, API reference, engineering blog, changelog, Stack Overflow tag, and 46 more developer resources.
46.0/100developing▬ flatAgent27/100agent awareFront door AI2/6
trace
Heartbeat100/100
alive
saas · Apache License 2.0
Full breakdown ↓
scored 2026-11-06 · rubric v0.27.0 · Show this score on your site →
Regulatory Posture applies to this provider. Its tags matched the
Horizontal (data, software, accessibility, platform) regime, so
Regulatory Posture carries 15 points of the composite.
If this regime is wrong for your business, say so on your
provider repo — the
applicability map is public and we will correct it.
Create-or-Update Ergonomics does not apply to this provider. The published contracts declare
no write operations, and a read-only API cannot create-or-update. The facet is excluded from this provider's
denominator entirely — not scored zero. A reference or data API is not deficient for being unable to
upsert.
The six quality facets above are damped to 85 points between them,
because the conditional facet above carries the other
15. That is why each facet's contribution is shown against a damped
maximum: raising a quality facet moves the composite by 85% of its nominal
weight, not 100%. The full arithmetic is at apis.io/rating/.
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Agent readiness — checks not met, largest first (exact, from this profile):
Machine-Readable Auth+10 pts — a served openid-configuration/oauth-authorization-server carrying `issuer` (served), else the securitySchemes class in the provider OpenAPIs — bound (mutualTLS, DPoP, Signature) > negotiable (oauth2 authorizationCode/clientCredentials, openIdConnect) > bearer (http bearer, apiKey)
Stable Error Semantics+8 pts — OpenAPI $refs a shared error schema across 4xx/5xx responses (verified), else common[].type includes ErrorCatalog / ErrorCodes / DeclineCodes
A2A Agent Card+8 pts — a2a/-a2a.yml manifest, graded on conformance.grade against A2A 1.0.0
Rate-Limit Signaling+7 pts — OpenAPI responses document X-RateLimit-* / RateLimit headers (verified), else a rate_limits artifact or RateLimits link (documented)
Delegated User Identity+6 pts — a served discovery document listing authorization_code in grant_types_supported (served), else an oauth2 authorizationCode flow or openIdConnect declared in an OpenAPI (documented)
6 more unmet checks in the Agent Readiness table above.
Kin Score — facets with the most composite points still available (weight × headroom):
Access Clarityscores 28.6 — up to +14.3 composite points
The Kin Score Market layer reads a provider inside its market:
its position, and how deep its integrations go. Depth is only comparable within a position. Provisional and unweighted:
not part of the Kin Score or agent readiness.
Registered MCP server and declares compatibility are report only — not weighted.
Undeclared means we found nothing we can read, so there is no number: we never infer integrations.
Standards this provider implements or carries. De facto ones are profiled and measured by the API Commons; formal ones come from the standards directory and are linked by the provider's own tags. The evidence column says how each claim was established — not that it was made.
The `bazel` command line tool is the primary user-facing surface of Bazel. It exposes commands such as `build`, `test`, `run`, `query`, `cquery`, `aquery`, `mod`, `fetch`, `info...
Bazel's build rules, macros, and module extensions are written in Starlark — a deterministic Python dialect. The Starlark Build API exposes the rule(), repository_rule(), module...
Bazel speaks the open Remote Execution API (REAPI), a gRPC protocol for content-addressable storage and distributed action execution. REAPI lets Bazel offload compile, test, and...
The Build Event Protocol (BEP) is Bazel's structured stream of build events — target configured, progress, test results, action executed, build finished — emitted during every i...
One build tool spans Java, C++, Go, Python, Rust, Swift, Kotlin, Scala, Android, iOS, Objective-C, and dozens of community-maintained language rules.
Hermetic, Reproducible Builds
Sandboxed action execution and explicit dependency declarations make Bazel builds reproducible across machines and CI runners.
Incremental Builds
Fine-grained action graph and Merkle-tree based caching mean only what changed gets rebuilt, even in monorepos with millions of targets.
Remote Caching and Execution
Bazel speaks the open Remote Execution API (REAPI) so teams can share a Content-Addressable Store and offload actions to a remote build farm.
Bzlmod External Dependencies
MODULE.bazel + the Bazel Central Registry replace the legacy WORKSPACE system with versioned, transitive, registry-resolved modules.
Starlark Extension Language
A deterministic Python-like DSL for writing custom rules, repository rules, module extensions, and aspects without touching Bazel internals.
Build Event Protocol
Every invocation emits a structured BEP/BES stream consumable by CI dashboards, observability tools, and flake detectors.
Query Languages
bazel query, cquery (configured), and aquery (action graph) let you inspect dependency graphs, configuration transitions, and the actual actions Bazel will run.
Toolchain Resolution
Platform-aware toolchain selection lets one BUILD graph target Linux, macOS, Windows, Android, iOS, and embedded targets from the same source tree.
Persistent Workers
Long-lived worker processes (javac, scalac, etc.) amortize JVM and compiler startup across many actions for faster incremental builds.
Bazel Central Registry
Default public index of Bazel modules at bcr.bazel.build with searchable UI at registry.bazel.build.
Bazelisk Version Launcher
Pins the exact Bazel version per project via .bazelversion so every contributor and CI runner uses the same build tool.
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Kin Score
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