Google Cloud Speech-to-Text API
Browse all Google APIs42
AI ReadinessFoundational (D-)42/100
Official vendor OpenAPI document · agent-readyAI/MLSpeechoauth211 EndpointsREST
For Agents
Transcribe speech audio to text with optional phrase-set bias. Supports short synchronous calls and long-running jobs for multi-minute recordings.
Use for: I want to transcribe an audio file to text, Submit a long audio file for asynchronous transcription, Get the status of a long-running speech recognition job, Create a phrase set to improve recognition of product names
Not supported: Does not handle text-to-speech synthesis, speaker diarization training, or live in-browser microphone capture - use for converting recorded or streamed audio to text only.
The Cloud Speech-to-Text API converts spoken audio into text using Google's speech recognition models. It supports synchronous recognition for short clips, long-running recognition for multi-minute audio passed by Cloud Storage URI, and adaptation through phrase sets and custom classes that bias the recogniser toward domain-specific vocabulary. Typical inputs are LINEAR16, FLAC, or OGG_OPUS audio with the language code declared on the request.
Install Jentic One Beta
Connect the Cloud Speech-to-Text API to your agent
Jentic One is a self-hosted execution layer for AI agents. It lets your agent call the Cloud Speech-to-Text API, 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%2Fspeech" | 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%2Fspeech" | 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 Cloud Speech-to-Text API.
Transcribe a short audio clip synchronously and return the recognised text and word-level confidence
Submit a long-running recognition job for audio stored in Cloud Storage and poll for results
Bias the recogniser toward domain vocabulary by attaching a phrase set or custom class
Manage phrase sets - collections of weighted phrases - at the project level
Manage custom classes that group named entities for reuse across phrase sets
Cancel or inspect long-running speech recognition operations
Use Cases
Patterns agents use Cloud Speech-to-Text API for, with concrete tasks.
★ Call Centre Transcription
Transcribe recorded customer support calls into searchable text for QA review. Calls are uploaded to Cloud Storage and submitted via POST /v1/speech:longrunningrecognize, which returns an operation handle. The job runs asynchronously and the resulting transcript is fetched via the operations endpoint, typically within minutes.
POST /v1/speech:longrunningrecognize with audio.uri=gs://calls/abc.flac and config.languageCode=en-US, then poll GET /v1/operations/{name} until done.
Voice Note Capture in a Field App
A mobile field service app records short voice notes and sends them to the Speech-to-Text API for synchronous transcription. POST /v1/speech:recognize accepts audio inline as base64 or by Cloud Storage URI and returns the transcript in the same response, suitable for clips up to about a minute long.
POST /v1/speech:recognize with audio.content=<base64 LINEAR16> and config.languageCode=en-GB; return the alternatives[0].transcript.
Domain-Adapted Medical Dictation
Improve recognition accuracy for clinicians by creating a phrase set containing common drug names, procedures, and anatomical terms. The phrase set is then referenced in each recognise call's adaptation config so the model is biased toward those terms during decoding.
POST /v1/{+parent}/phraseSets with phrases=[{value:'amoxicillin',boost:15},...], then call recognize with adaptation.phraseSets=['projects/p/locations/global/phraseSets/meds'].
AI Agent Voice-Driven Workflow
An AI agent receives a voice message from a user, transcribes it via the Speech-to-Text API through Jentic, and then routes the transcript to its downstream reasoning step. The agent searches for the recognise operation, loads the schema, and executes - Jentic handles auth so the agent never sees the underlying credentials.
Search Jentic for 'transcribe an audio file', execute POST /v1/speech:recognize with the user's audio content and languageCode='en-US', then pass alternatives[0].transcript to the next reasoning step.
Key Endpoints
11 endpoints — the cloud speech-to-text api converts spoken audio into text using google's speech recognition models.
METHOD
PATH
DESCRIPTION
POST
/v1/speech:recognize
Synchronously transcribe a short audio clip
POST
/v1/speech:longrunningrecognize
Submit a long audio file for asynchronous transcription
GET
/v1/operations
List long-running recognition operations
GET
/v1/operations/{+name}
Get the status and result of a long-running recognition job
GET
/v1/{+parent}/phraseSets
List phrase sets in a project location
GET
/v1/{+parent}/customClasses
List custom classes in a project location
POST
/v1/speech:recognize
Synchronously transcribe a short audio clip
POST
/v1/speech:longrunningrecognize
Submit a long audio file for asynchronous transcription
GET
/v1/operations
List long-running recognition operations
GET
/v1/operations/{+name}
Get the status and result of a long-running recognition job
GET
/v1/{+parent}/phraseSets
List phrase sets in a project location
GET
/v1/{+parent}/customClasses
List custom classes in a project location
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.
C
Cloud Speech-to-Text API
- Foundational (D-)42/100
60
Foundational Compliance56
Developer Experience & Jentic Compatibility20
AI-Readiness & Agent Experience94
Agent Usability63
Security59
AI DiscoverabilityPowered by JenticScoring Framework 1.0.0 | Scoring Engine 0.4.0
Show dimension breakdown
60
Foundational Compliance
Base layer of spec validity and structural soundness.
Grade: B-Signals: 4
80%
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).
60%
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
79%
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.
63
Security
Trust, risk posture, and security compliance.
Grade: B-Signals: 1
62%
Authentication Strength
Average quality of security schemes based on authentication method strength (weakest link for OAuth2).
59
AI Discoverability
Findability, semantic richness, and reasoning readiness.
Grade: C+Signals: 1
59%
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 Cloud Speech-to-Text API by hand means configuring a service account, minting OAuth access tokens against speech.googleapis.com, and polling long-running operations yourself. Through Jentic you install once, import the Cloud Speech-to-Text API from the API Directory, store the OAuth credential once, and your agent calls it.
Permission scoping
Speech-to-Text puts the project resource in the URL path for phrase sets and custom classes (/v1/{parent}/phraseSets), and recognition runs against a fixed endpoint, so limit the agent to the operations it needs, such as speech.recognize and reading operation status. You choose the operations it may call, so managing phrase sets or custom classes is not included unless you add them.
Credential isolation
Your Speech-to-Text OAuth credential is stored once, encrypted, by your own Jentic One instance and injected at execution time. It never enters the agent's prompt, logs, or context.
Intent-based discovery
Agents search Jentic by intent such as 'transcribe an audio file' or 'submit a long audio for transcription', and Jentic returns the matching Speech-to-Text 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 Cloud Speech-to-Text API through Jentic.
What authentication does the Cloud Speech-to-Text API use?
The Cloud Speech-to-Text API uses OAuth 2.0 with the cloud-platform scope. Through Jentic, OAuth credentials are stored in your Jentic One instance and exchanged for short-lived access tokens, so service-account JSON keys never enter the agent context.
Can I transcribe long audio files with the Speech-to-Text API?
Yes. POST /v1/speech:longrunningrecognize accepts a Cloud Storage URI and returns an operation that can be polled via GET /v1/operations/{name}. This is the recommended path for any audio longer than about 60 seconds, where the synchronous recognise endpoint times out.
What are the rate limits for the Cloud Speech-to-Text API?
Default project quotas are 900 requests per minute and 480 minutes of audio per minute, with stricter limits on long-running submissions. Quotas are visible in the Google Cloud Console under IAM and admin > Quotas and can be raised on request.
How do I improve recognition of brand or technical terms?
Create a phrase set via POST /v1/{+parent}/phraseSets with the target terms and a boost value, then reference the phrase set in the adaptation field of the recognise request. This biases the recogniser toward the supplied vocabulary without retraining a model.
How do I run transcription through Jentic?
Search Jentic for 'transcribe an audio file', load the speech.recognize or speech.longrunningrecognize schema, and execute. Jentic returns the operation result for sync calls and the long-running operation handle for async jobs, which the agent can poll via the operations endpoint.
Is the Cloud Speech-to-Text API free?
Google offers 60 minutes of free transcription per month, after which usage is billed per 15-second increment, with different rates for standard, video, and medical models. Phrase set storage is free; data adaptation usage is billed at standard rates.
Can I limit what my agent is allowed to do with the Cloud Speech-to-Text API?
Yes. Because you run Jentic One yourself, your own rules decide which Speech-to-Text operations and credentials the agent may use. You can allow it only what it needs, such as speech.recognize for short clips, speech.longrunningrecognize for long audio, and reading operation status, while leaving out phrase set and custom class management unless you explicitly add those. The stored OAuth credential is injected at execution time and never enters the agent's prompt or logs.
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