Gmail

Under an hour to a working test app; weeks to months to production for an agent that reads mail. gmail.readonly and gmail.modify are restricted scopes: verification plus an annual third-party CASA assessment. A send-only agent (gmail.send) scores 3: sensitive-scope verification, no CASA.

Difficulty

5/5 · Very hard

Approval

scope verification

Confidence

medium

Test before approval

Yes

Why this score

• CASA third-party security assessment (annual) (security-assessment, weight 5)

send-only path: 3/5 · Moderate

• Pick the narrowest Gmail scope (both) — done when: Scope list and profile (send-only vs read/modify) are fixed.
• Create the project and OAuth client (human) — done when: A test user completes consent and you get a token.
• Brand and scope verification (both) — done when: Brand and scope verification approved.

• criticalReading mail (gmail.readonly / gmail.modify) needs restricted-scope verification and a paid, annual third-party CASA assessment. (Production-ready)Workaround: Ship a send-only agent first (gmail.send), or sell to Workspace orgs whose admins mark the app Trusted.An agent can help with this.
• highIn Testing mode every test user's authorization expires after 7 days, so pilots silently disconnect weekly. (Pilot-ready)Workaround: Build a re-consent prompt, or have the customer's Workspace admin mark the app Trusted.An agent can help with this.
• mediumVerification needs a homepage on a verified domain you own; a login page or unowned domain fails. (Production-ready)Workaround: Publish a real homepage and privacy policy on your domain before submitting.An agent can help with this.

• Google Cloud project with the Gmail API enabled (human · Dev-ready): Google recommends separate projects for testing and production.
• Verified domain, homepage and privacy policy (human · Production-ready): The homepage must be on a verified domain you own (verified in Search Console by a project Owner or Editor) and describe the app.
• Demo video (human · Production-ready): Unlisted YouTube video showing the OAuth grant flow in English, the app name on the consent screen, and each scope in use.
• CASA assessor (restricted scopes only) (human · Production-ready): Contract an App Defense Alliance-authorized assessor once Google tells you to start.

• Testing mode: 100 test users, 7-day refresh tokens (testing cap)Applies when: until the app is published. Required for Pilot-ready.
• Sensitive scope verification (gmail.send) (scope review)Applies when: sensitive scopes in production. Required for Production-ready.Duration: Brand verification first: automated check usually a few minutes; manual review usually 2-3 business days. Scope review time beyond that is not published.primarysource
• Restricted scope verification (gmail.readonly / gmail.modify) (scope review)Applies when: read/modify profile (default for AI agents). Required for Production-ready. Skipped for: send-only.Duration: Several weeks, possibly several months.primarysource
• CASA third-party security assessment (annual) (security assessment)Applies when: restricted Gmail scopes. Required for Production-ready. Skipped for: send-only.Cost: Paid to the assessor. One vendor (Secusy) lists AL1 at $499–$3,000/yr and AL2 at about $5,400/yr.secondaryReported by developers, not a commitmentsourceRecurring: Annual recertification; apps are assigned AL1 or AL2.primarysource

1. Pick the narrowest Gmail scope (decide · both · ~15 min)
   • If the agent only sends, request gmail.send only (sensitive, no CASA).
   • If it must read mail, budget for restricted-scope verification and CASA.
   Done when: Scope list and profile (send-only vs read/modify) are fixed.
2. Create the project and OAuth client (create · human · ~30 min)
   • Create a project, enable the Gmail API.
   • Google Auth Platform → Branding (name, support email, logo, homepage, privacy policy, authorized domains).
   • Audience: External, Testing; add test users.
   • Clients → Web application, with the Composio redirect URI.
   Done when: A test user completes consent and you get a token.
3. Brand and scope verification (submit · both)
   • Verify the domain in Search Console.
   • Record the demo video and write per-scope justifications.
   • Submit in the Verification Center and answer Google's emails.
   Done when: Brand and scope verification approved.
4. CASA assessment (restricted scopes) (submit · human)
   • When Google asks, engage an authorized assessor and complete the assessment.
   • Calendar the annual revalidation.
   Done when: Letter of Validation submitted and app verified.

Redirect URIs:

Adding redirect URLs or changing the product name after verification can trigger re-verification.secondaryReported by developers, not a commitmentsource

PKCE:

Supported: plain and S256.tested · probesource

Token lifetime:

In Testing mode, refresh tokens expire 7 days after consent. Otherwise a refresh token stops working after 6 months unused, or on password change when it holds Gmail scopes.primarysource

Refresh:

Max 100 refresh tokens per Google Account per OAuth client; older ones are revoked past the limit.primarysource

Rate limits:

Unverified apps: 100 new users in total after the unverified-app screen is shown.primarysource

• GET https://accounts.google.com/.well-known/openid-configuration → 200OIDC discovery: authorization_endpoint https://accounts.google.com/o/oauth2/v2/auth, PKCE plain and S256. (2026-10-19T20:37:19Z)
• GET https://accounts.google.com/o/oauth2/v2/auth?client_id=oauth-atlas-probe&redirect_uri=https%3A%2F%2Fexample.com%2Fcb&response_type=code&scope=https%3A%2F%2Fwww.googleapis.com%2Fauth%2Fgmail.readonly → 302 → https://accounts.google.com/signin/oauth/error?authError=Cg5pbnZhbGlkX2NsaWVudBIfVGhlIE9BdXRoIGNsaWVudCB3YXMgbm90IGZvdW5kLiCRAw&flowName=GeneralOAuthFlow&client_id=oauth-atlas-probeFake client rejected up front: authError decodes to "invalid_client: The OAuth client was not found." (2026-10-19T20:37:19Z)

• [ev-testing] Testing mode: up to 100 test users; authorizations expire after 7 days. primary high confidence

  Authorizations by a test user will expire seven days from the time of consent.

  https://support.google.com/cloud/answer/15549945official-doc · retrieved 2026-10-19T20:43:42Z
• [ev-scopes] gmail.send is sensitive; gmail.readonly and gmail.modify are restricted. primary high confidence

  Restricted scopes Scope code Description https://mail.google.com/ Read, compose, send, and permanently delete all your email from Gmail.

  https://developers.google.com/workspace/gmail/api/auth/scopesofficial-doc · retrieved 2026-10-19T20:43:54Z
• [ev-casa] Restricted-scope apps need an annual security assessment (CASA, AL1 or AL2). primary high confidence

  To maintain the security of Google users' data, applications requesting access to restricted scopes must undergo an annual security assessment.

  https://support.google.com/cloud/answer/13465431official-doc · retrieved 2026-10-19T20:43:49Z
• [ev-restricted-time] Restricted-scope verification can take several weeks. primary medium confidence

  For this reason, the restricted scopes verification process can potentially take several weeks to complete.

  https://developers.google.com/identity/protocols/oauth2/production-readiness/restricted-scope-verificationofficial-doc · retrieved 2026-10-19T20:43:44Z
• [ev-brand] Brand verification: automated in minutes, manual review usually 2-3 business days. primary high confidence

  The automated brand verification process typically takes a few minutes after you click the Verify Branding button.

  https://developers.google.com/identity/protocols/oauth2/production-readiness/brand-verificationofficial-doc · retrieved 2026-10-19T20:44:00Z
• [ev-homepage] The homepage must be on a verified domain you own. primary high confidence

  The homepage must be hosted on a verified domain you own

  https://support.google.com/cloud/answer/13464321policy · retrieved 2026-10-19T20:43:46Z
• [ev-video] The demo video is uploaded to YouTube as Unlisted. primary high confidence

  Upload the video to YouTube Studio and set Visibility as Unlisted .

  https://developers.google.com/identity/protocols/oauth2/production-readiness/restricted-scope-verificationofficial-doc · retrieved 2026-10-19T20:43:44Z
• [ev-trusted] A Workspace admin marking the app Trusted lifts the test-user cap and 7-day expiry for that org. primary high confidence

  When a Google Workspace administrator marks an app as Trusted , it is treated as an internal application for that organization.

  https://developers.google.com/identity/protocols/oauth2/production-readiness/overviewofficial-doc · retrieved 2026-10-19T20:43:58Z
• [ev-casa-cost] CASA AL2 about $5,400/yr (one vendor, Secusy); AL1 $499–$3,000. secondary low confidence Reported by developers, not a commitmenthttps://www.secusy.ai/blog/google-casa-assessment-costpricing · retrieved 2026-10-20
• [ev-probe-authorize] Fake client_id is rejected with invalid_client at the authorize endpoint. tested high confidencehttps://accounts.google.com/o/oauth2/v2/authtest · retrieved 2026-10-19T20:37:19Z

• Actual end-to-end time for restricted-scope verification plus CASA: Google gives "several weeks" to "several months", no upper bound.
• CASA price: only vendor price lists (secondary); Google publishes none.
• Whether Composio's managed Gmail app is verified for restricted scopes (not public to us).
• Sensitive-only (gmail.send) review duration beyond brand verification: not published.

• 2026-10-20: Google CASA tiers — CASA "Tier 2 / Tier 3". → Assurance levels AL1 / AL2, assigned by Google; annual revalidation. (Google renamed the tiers.)