Google API Discovery Service
Browse all Google APIs44
AI ReadinessFoundational (D)44/100
Official vendor OpenAPI document · agent-readyDeveloper ToolsPackage Registrynone2 EndpointsREST
For Agents
Enumerate every Google API and fetch its machine-readable description so tools, SDKs, and agents can self-bootstrap.
Use for: List all Google APIs available via the Discovery service, Get the Discovery document for a specific Google API, Find the OAuth scopes for the Google Calendar API, Retrieve the schema for the Drive v3 files resource
Not supported: Does not enable APIs, manage quotas, or proxy actual API calls - use only for reading the Google API directory and Discovery REST descriptions.
Google's API Discovery Service is the meta-API that describes every other Google API. Two endpoints expose the directory of supported APIs and the machine-readable Discovery REST description for each one - methods, parameters, schemas, scopes, and base URLs. Client library generators, IDE tooling, and Jentic itself use this surface to bootstrap integrations against the entire googleapis.com surface without hand-written specs.
Install Jentic One Beta
Connect the API Discovery Service to your agent
Jentic One is a self-hosted execution layer for AI agents. It lets your agent call the API Discovery Service, or any other public or private API you need. You set the rules, the agent never sees your credentials, and every call is logged.
Two steps, two machines. Install the instance in a safe environment, then register your agent from wherever it runs.
1
Step 1: Jentic One Host machine
# On the machine that will host your Jentic One instance:
curl -fsSL "https://jentic.com/install.sh?src=apis&api=%2Fapis%2Fgoogleapis.com%2Fdiscovery" | sh2
Step 2: Agent machine
# On the machine where your agent runs (keep this separate from the instance):
curl -fsSL "https://jentic.com/install.sh?src=apis&api=%2Fapis%2Fgoogleapis.com%2Fdiscovery" | sh
jentic register # connects your agent to your Jentic One instanceJentic One is in public beta. The setup above keeps your agent separate from the instance, which is what you want before using real credentials: an agent running as the same OS user as Jentic One can read its stored keys directly. Just evaluating? A single local install is fine to start. See the secure deployment guide for the tiers.
Capabilities
What an agent can do with API Discovery Service API.
List the directory of all Google APIs available through Discovery
Fetch the full Discovery REST description for any Google API and version
Extract method definitions, parameters, and request/response schemas for SDK generation
Resolve OAuth scopes and base URLs declared by a target API
Filter the directory by preferred or all-versions to find the latest release
Use Cases
Patterns agents use API Discovery Service API for, with concrete tasks.
★ SDK and Client Library Generation
Tooling teams call /apis to discover every Google API, then /apis/{api}/{version}/rest to pull the Discovery document for each. The descriptions feed code generators that emit typed clients in Python, Go, Java, and TypeScript. This is exactly how the official Google API Client Libraries are produced.
Call /apis with preferred=true, then for the calendar v3 entry call /apis/calendar/v3/rest and extract every method's id, path, and parameter schema.
Scope and Permission Inventory
Security and platform teams use the Discovery API to inventory every OAuth scope declared by every Google API in a project's footprint. Pulling the full directory and extracting auth.oauth2.scopes from each Discovery doc gives a complete map of what tokens can do - useful for least-privilege reviews and risk register updates.
Call /apis with preferred=true and for each entry fetch /apis/{api}/{version}/rest, extract auth.oauth2.scopes, then return a deduplicated scope list.
Spec-Driven Integration Bootstrapping
Integration platforms (including Jentic) use Discovery as the source-of-truth for converting Google APIs into modern OpenAPI specs. Pulling /apis once on schedule produces the directory; pulling per-API REST documents produces the operational shape; conversion logic translates that into OpenAPI 3.x for tooling and agent runtimes.
Fetch /apis/drive/v3/rest, then transform the returned Discovery REST document into an OpenAPI 3 paths object preserving operationId, parameters, and request/response schemas.
Agent-Driven API Lookup
Through Jentic, an AI agent that needs to operate on a Google API it has not seen before can call the Discovery service to fetch the description on demand, then use it to build a request - all without OAuth, since Discovery is unauthenticated.
Use Jentic to search 'list Google APIs', load the schema for /apis, and execute it with preferred=true to enumerate the catalogue.
Key Endpoints
2 endpoints — google's api discovery service is the meta-api that describes every other google api.
METHOD
PATH
DESCRIPTION
GET
/apis
List the directory of Google APIs
GET
/apis/{api}/{version}/rest
Fetch the Discovery REST document for a specific API and version
GET
/apis
List the directory of Google APIs
GET
/apis/{api}/{version}/rest
Fetch the Discovery REST document for a specific API and version
Jentic AI Readiness Score
This API is usable in Jentic One now. Its AI-readiness score against Jentic's framework shows where it stands today and where improvements would make it even easier for agents to use.
A
API Discovery Service
- Foundational (D)44/100
70
Foundational Compliance56
Developer Experience & Jentic Compatibility20
AI-Readiness & Agent Experience94
Agent Usability100
Security63
AI DiscoverabilityPowered by JenticScoring Framework 1.0.0 | Scoring Engine 0.4.0
Show dimension breakdown
70
Foundational Compliance
Base layer of spec validity and structural soundness.
Grade: A-Signals: 4
82%
Lint Results
Aggregated quality score from linter diagnostics, weighted by severity.
100%
Resolution Completeness
Percentage of `$ref` references that resolve successfully.
0%
Specification Validity
Checks whether the API description parses successfully and conforms to its declared specification (e.g., OpenAPI).
100%
Structural Integrity
Structural correctness score based on schema issues using logarithmic dampening.
56
Developer Experience & Jentic Compatibility
Clarity, completeness, and ingestion readiness for developers and tooling.
Grade: CSignals: 4
0%
Example Density
How richly the API is illustrated with examples.
100%
Example Validity
Percentage of examples that conform to their schemas.
25%
Response Coverage
Percentage of operations with complete response definitions (success, client error, server error).
100%
Tooling Readiness
Health of API ingestion, bundling, and resolution within Jentic pipelines.
20
AI-Readiness & Agent Experience
Semantic breadth, depth, and agent comprehension for AI systems.
Grade: FSignals: 4
78%
Description Coverage
Coverage of descriptions across API elements.
0%
Error Standardization
Coverage of RFC 9457 Problem Details for error responses.
0%
OperationId Quality
Coverage, uniqueness, and casing consistency of operationIds for AI inference.
0%
Summary Coverage
Coverage of summaries across operations/tags/info.
94
Agent Usability
Functional utility, complexity comfort, and AI orchestration readiness.
Grade: A+Signals: 1
94%
Complexity Comfort
Agent comfort level based on API operational and structural complexity.
100
Security
Trust, risk posture, and security compliance.
Grade: A+Signals: 1
100%
Authentication Strength
Average quality of security schemes based on authentication method strength (weakest link for OAuth2).
63
AI Discoverability
Findability, semantic richness, and reasoning readiness.
Grade: B-Signals: 1
62%
Descriptive Richness
Clarity and depth of descriptions across API elements.
Score it yourself
Every API in the directory is allowlisted, so you can re-score it with no key required.
npx @jentic/api-scorecard-cli score <openapi-url>Why Jentic?
What agents get from Jentic-routed access to this vendor.
Setup
Wiring the API Discovery Service by hand means handling its public unauthenticated calls against the Google discovery host and parsing the directory and REST descriptions yourself. Through Jentic you install once, import the API Discovery Service from the API Directory, and your agent calls it without extra plumbing.
Permission scoping
This service reads the Google API directory and takes its API and version in the request, so scope by operations: limit the agent to the operations it needs, such as listing APIs or reading a single REST description. You choose the operations it may call, and it reads only what you name.
Credential isolation
The API Discovery Service needs no credential, so there is nothing to store. Requests run through your own Jentic One instance, and no secret enters the agent's prompt, logs, or context.
Intent-based discovery
Agents search Jentic by intent such as 'list available Google APIs' or 'read a Discovery REST description', and Jentic returns the matching Discovery operation with its input schema so the agent calls the right endpoint without browsing the reference docs.
Related APIs
Alternatives and complements available in the Jentic catalogue.
FAQs
Specific to using API Discovery Service API through Jentic.
What authentication does the Google API Discovery Service use?
None. Both /apis and /apis/{api}/{version}/rest are public, unauthenticated GETs. Through Jentic, the call runs in the sandboxed runner without any vault credentials touching the request.
Can I get the OAuth scopes for any Google API through Discovery?
Yes. Fetch /apis/{api}/{version}/rest and read auth.oauth2.scopes - every scope the API declares is listed there with its description, which is the canonical source for least-privilege OAuth setup.
What are the rate limits for the API Discovery Service?
Google does not publish strict per-second limits for Discovery, but unreasonable polling can be throttled. Cache responses locally and re-fetch on a slow cadence (daily for the directory, weekly per-API) instead of calling on every request.
How do I list every Google API through Jentic?
Search 'list Google APIs', load the schema for /apis, then execute it. To filter to the recommended version of each API, pass preferred=true in the query parameters.
Is the Discovery REST format the same as OpenAPI?
No. Discovery is Google's own format that pre-dates OpenAPI 3. It contains similar concepts (resources, methods, parameters, schemas) but uses different field names and structures. Tools convert it to OpenAPI for compatibility with modern toolchains.
Is the Discovery Service free?
Yes. There is no charge for Discovery calls and you do not need an API key or OAuth token to read the directory or any individual Discovery REST document.
Can I limit what my agent is allowed to do with the API Discovery Service?
Yes. Because you run Jentic One yourself, your own rules decide which of the two Discovery operations the agent may call: listing the Google API directory or reading a single API's Discovery REST description. You can allow only the read that a task needs, so an agent limited to reading one REST description cannot enumerate the whole directory. The service is unauthenticated, so there are no credentials to grant, and the agent reads only the API and version you name.
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