Voice AI Agent-Readiness Index
Last checked: 2026-09-16. This index compares the public tools a coding agent can use to build a voice application. It does not measure call quality or rank vendors.
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Methodology
- Published first-party documentation and repositories, inspected September 16, 2026. No authenticated tools/list requests or account operations were executed.
- Hosted operations MCP means a vendor-hosted server that reads or changes account resources. Docs-only MCP and a voice agent calling external MCP tools are separate capabilities.
- Tool counts describe each documented hosted catalog, including docs tools where bundled, not quality, permissions, or measured task success. Separate docs-only catalogs are not account-tool counts. Skill counts label their scope, exclude generated mirrors and explicitly experimental workflows, and distinguish a docs skill resource from a multi-skill pack.
- Yes means the linked source establishes availability. No is used only for an explicit limitation or the known ThunderPhone release snapshot. Unknown means the inspected source did not establish the claim; it is not evidence of absence.
- Directory listing means an official connector or plugin directory entry. A GitHub marketplace, plugin package, or manual custom connector does not establish listing approval.
- MCP Registry listing is separate from Claude and OpenAI directories. Yes requires a vendor-owned namespace or repository in the registry result. Search results for third-party integrations do not establish first-party publication; an empty search is not proof of absence. Vapi search uses latest versions to avoid pagination over unrelated historical releases.
- SDK scope is labeled: REST clients, framework runtimes, and browser/mobile clients are different surfaces. Vendor-wide tooling does not imply complete ConversationRelay coverage.
- ThunderPhone publishes this index and is included in it. There is no aggregate score or preferred-vendor ranking. Review every source and date before choosing a platform.
Each cell links to the inspected source and records its checked-on date. For an unknown, the link shows where we looked, not proof that the capability is absent. Published counts can differ from the tools enabled for a particular key.
Hosted account operations
| Vendor | Hosted operations MCP | MCP tool count | MCP authentication |
|---|---|---|---|
| ThunderPhone | Yes — https://api.thunderphone.com/v1/mcp. Source (2026-09-16) | Yes — 59 documented tools. Source (2026-09-16) | Yes — API key (Bearer). Source (2026-09-16) |
| Vapi | Yes — https://mcp.vapi.ai/mcp. Source (2026-09-16) | Yes — 10 documented core tools (not a live enumeration). Source (2026-09-16) | Yes — API key (Bearer). Source (2026-09-16) |
| Retell | Yes — https://mcp.retellai.com. Source (2026-09-16) | Unknown — Unknown: guide lists operation categories, not an exhaustive tool count. Source (2026-09-16) | Yes — API key (Bearer). Source (2026-09-16) |
| ElevenLabs | Yes — https://api.elevenlabs.io/v1/mcp. Source (2026-09-16) | Unknown — Unknown: hosted-server guide describes capabilities, not an exhaustive tool count. Source (2026-09-16) | Yes — OAuth (hosted server); local server uses API key. Source (2026-09-16) |
| Bland | Yes — https://api.bland.ai/v1/mcp. Source (2026-09-16) | Yes — 42 documented tools including docs and setup; 3 prompts excluded. Source (2026-09-16) | Yes — API key (Bearer). Source (2026-09-16) |
| LiveKit Agents | Unknown — Unknown: docs MCP is documented; hosted account-operations MCP and its catalog/auth are not established. Source (2026-09-16) | Unknown — Unknown: docs MCP is documented; hosted account-operations MCP and its catalog/auth are not established. Source (2026-09-16) | Unknown — Unknown: docs MCP is documented; hosted account-operations MCP and its catalog/auth are not established. Source (2026-09-16) |
| Pipecat | Unknown — Unknown: docs MCP is documented; hosted account-operations MCP and its catalog/auth are not established. Source (2026-09-16) | Unknown — Unknown: docs MCP is documented; hosted account-operations MCP and its catalog/auth are not established. Source (2026-09-16) | Unknown — Unknown: docs MCP is documented; hosted account-operations MCP and its catalog/auth are not established. Source (2026-09-16) |
| Twilio ConversationRelay | No — Inspected Twilio MCP is read-only docs; API execution listed as planned. Source (2026-09-16) | Unknown — Unknown: account-operations catalog/auth not applicable to the documented docs-only server. Source (2026-09-16) | Unknown — Unknown: account-operations catalog/auth not applicable to the documented docs-only server. Source (2026-09-16) |
Documentation access
| Vendor | Docs MCP | llms.txt | Markdown docs alternates | Public OpenAPI |
|---|---|---|---|---|
| ThunderPhone | Yes — https://thunderphone.com/docs/mcp; no authentication. Source (2026-09-16) | Yes — https://thunderphone.com/llms.txt. Source (2026-09-16) | Yes — Append .md to a docs page. Source (2026-09-16) | Yes — https://thunderphone.com/docs/openapi.json. Source (2026-09-16) |
| Vapi | Yes — https://docs.vapi.ai/_mcp/server; no authentication. Source (2026-09-16) | Yes — https://docs.vapi.ai/llms.txt. Source (2026-09-16) | Yes — Append .md to a docs page. Source (2026-09-16) | Yes — Public OpenAPI 3.1 (JSON and YAML) linked from the docs index. Source (2026-09-16) |
| Retell | Yes — https://docs.retellai.com/mcp; documentation search and retrieval. Source (2026-09-16) | Yes — https://docs.retellai.com/llms.txt. Source (2026-09-16) | Yes — Append .md to a docs page. Source (2026-09-16) | Yes — Public OpenAPI 3.0.3 REST specification. Source (2026-09-16) |
| ElevenLabs | Yes — https://elevenlabs.io/_mcp/server. Source (2026-09-16) | Yes — https://elevenlabs.io/docs/llms.txt. Source (2026-09-16) | Yes — Append .md to a docs page. Source (2026-09-16) | Yes — Public OpenAPI 3.1 REST specification. Source (2026-09-16) |
| Bland | Yes — https://docs.bland.ai/mcp. Source (2026-09-16) | Yes — https://docs.bland.ai/llms.txt. Source (2026-09-16) | Yes — Append .md to a docs page. Source (2026-09-16) | Unknown — Unknown: no public specification URL established in docs index, API guide or docs MCP; checked root spec URLs return 404. Source (2026-09-16) |
| LiveKit Agents | Yes — https://docs.livekit.io/mcp; no authentication. Source (2026-09-16) | Yes — https://docs.livekit.io/llms.txt. Source (2026-09-16) | Yes — Append .md or request text/markdown. Source (2026-09-16) | Unknown — Unknown: reference documents Twirp server APIs; no public OpenAPI specification established. Source (2026-09-16) |
| Pipecat | Yes — Hosted https://docs.pipecat.ai/mcp; local Context Hub is another docs option. Source (2026-09-16) | Yes — https://docs.pipecat.ai/llms.txt. Source (2026-09-16) | Yes — Docs index links to .md pages. Source (2026-09-16) | Yes — Public OpenAPI 3.0 specification for Pipecat Cloud REST API; not the local framework. Source (2026-09-16) |
| Twilio ConversationRelay | Yes — https://mcp.twilio.com/docs; no authentication (public beta). Source (2026-09-16) | Yes — https://www.twilio.com/docs/llms.txt. Source (2026-09-16) | Yes — Docs available as .md. Source (2026-09-16) | Yes — Public Twilio API specs; not a complete ConversationRelay WebSocket schema. Source (2026-09-16) |
Skills
| Vendor | Skills pack | Skill count | Skills install command |
|---|---|---|---|
| ThunderPhone | Yes — Available. Source (2026-09-16) | Yes — 20 canonical skills. Source (2026-09-16) | Yes — npx skills add thunderphone/skills. Source (2026-09-16) |
| Vapi | Yes — Available. Source (2026-09-16) | Yes — 11 standard skills; experimental workflow excluded. Source (2026-09-16) | Yes — npx skills add VapiAI/skills. Source (2026-09-16) |
| Retell | Yes — Published skill.md and a docs MCP skill resource; not a multi-skill repository. Source (2026-09-16) | Yes — 1 docs skill resource; not a count of a separate skills pack. Source (2026-09-16) | Unknown — Unknown: skill.md is public; no package installation command documented. Source (2026-09-16) |
| ElevenLabs | Yes — Available. Source (2026-09-16) | Yes — 10 skills. Source (2026-09-16) | Yes — npx skills add elevenlabs/skills. Source (2026-09-16) |
| Bland | Yes — Bland plugin bundles skills. Source (2026-09-16) | Yes — 12 named plugin skills; separate docs skill resource not included. Source (2026-09-16) | Yes — /plugin marketplace add CINTELLILABS/bland-plugins; then /plugin install bland@bland. Source (2026-09-16) |
| LiveKit Agents | Yes — Available. Source (2026-09-16) | Yes — 2 skills. Source (2026-09-16) | Yes — npx skills add livekit/agent-skills. Source (2026-09-16) |
| Pipecat | Yes — Published skill.md and a docs MCP skill resource; not a multi-skill repository. Source (2026-09-16) | Yes — 1 docs skill resource; not a count of a separate skills pack. Source (2026-09-16) | Unknown — Unknown: skill.md is public; no package installation command documented. Source (2026-09-16) |
| Twilio ConversationRelay | Yes — Twilio developer kit (vendor-wide public beta). Source (2026-09-16) | Yes — 15 named skills in the documented tables (vendor-wide). Source (2026-09-16) | Yes — claude plugin install twilio-developer-kit. Source (2026-09-16) |
Official directory listings
| Vendor | Claude connector directory | OpenAI plugin directory | MCP Registry listing |
|---|---|---|---|
| ThunderPhone | No — Not listed in the known release snapshot. Source (2026-09-16) | No — Not listed in the known release snapshot. Source (2026-09-16) | Yes — io.github.thunderphone/thunderphone. Source (2026-09-16) |
| Vapi | Unknown — Unknown: not established by the docs index and linked guides checked. Source (2026-09-16) | Unknown — Unknown: not established by the docs index and linked guides checked. Source (2026-09-16) | Unknown — Unknown: no first-party listing identified in completed vendor-name search; third-party or unrelated results do not establish vendor publication. Source (2026-09-16) |
| Retell | Unknown — Unknown: not established by the docs index and linked guides checked. Source (2026-09-16) | Unknown — Unknown: not established by the docs index and linked guides checked. Source (2026-09-16) | Unknown — Unknown: no first-party listing identified in completed vendor-name search; third-party or unrelated results do not establish vendor publication. Source (2026-09-16) |
| ElevenLabs | Yes — Listed; linked by vendor to claude.ai/directory/connectors/elevenlabs. Source (2026-09-16) | Unknown — Unknown: manual ChatGPT setup is documented; official directory approval not established. Source (2026-09-16) | Yes — io.elevenlabs/mcp. Source (2026-09-16) |
| Bland | Unknown — Unknown: not established by the docs index and linked guides checked. Source (2026-09-16) | Unknown — Unknown: not established by the docs index and linked guides checked. Source (2026-09-16) | Unknown — Unknown: no first-party listing identified in completed vendor-name search; third-party or unrelated results do not establish vendor publication. Source (2026-09-16) |
| LiveKit Agents | Unknown — Unknown: not established by the docs index and linked guides checked. Source (2026-09-16) | Unknown — Unknown: not established by the docs index and linked guides checked. Source (2026-09-16) | Unknown — Unknown: no first-party listing identified in completed vendor-name search; third-party or unrelated results do not establish vendor publication. Source (2026-09-16) |
| Pipecat | Unknown — Unknown: not established by the docs index and linked guides checked. Source (2026-09-16) | Unknown — Unknown: not established by the docs index and linked guides checked. Source (2026-09-16) | Unknown — Unknown: no first-party listing identified in completed vendor-name search; third-party or unrelated results do not establish vendor publication. Source (2026-09-16) |
| Twilio ConversationRelay | Yes — Vendor links to official Twilio connector and plugin entries. Source (2026-09-16) | Yes — Vendor documents Twilio developer kit in Codex Plugins; ChatGPT listing unknown. Source (2026-09-16) | Unknown — Unknown: no first-party listing identified in completed vendor-name search; third-party or unrelated results do not establish vendor publication. Source (2026-09-16) |
SDKs and command-line tools
| Vendor | SDK languages | CLI |
|---|---|---|
| ThunderPhone | No — No standalone REST SDK published in this snapshot; REST and OpenAPI available. Source (2026-09-16) | No — No standalone product CLI published in this snapshot. Source (2026-09-16) |
| Vapi | Yes — Python, TypeScript (examples in skills). Source (2026-09-16) | Yes — vapi mcp setup. Source (2026-09-16) |
| Retell | Yes — Python, TypeScript / Node.js. Source (2026-09-16) | Yes — retell; npm install --global @retell-ai/retell-cli. Source (2026-09-16) |
| ElevenLabs | Yes — Python, JavaScript / TypeScript. Source (2026-09-16) | Yes — elevenlabs; npm install -g @elevenlabs/cli. Source (2026-09-16) |
| Bland | Yes — JavaScript / TypeScript web-agent SDK; browser calls, not a full REST client. Source (2026-09-16) | Yes — npx bland-cli; includes local bland mcp. Source (2026-09-16) |
| LiveKit Agents | Yes — Python, Node.js (Agents framework). Source (2026-09-16) | Yes — lk; includes lk docs. Source (2026-09-16) |
| Pipecat | Yes — Python framework; JavaScript, React, React Native, iOS, Android, C++ clients. Source (2026-09-16) | Yes — pipecat / pc; uv tool install "pipecat-ai[cli]". Source (2026-09-16) |
| Twilio ConversationRelay | Yes — Vendor-wide REST SDKs: C#/.NET, Java, Node.js, PHP, Python, Ruby, Go; ConversationRelay still uses an application WebSocket server. Source (2026-09-16) | Yes — Twilio CLI; npm install -g twilio-cli (vendor-wide API tooling). Source (2026-09-16) |
Recheck or correct a cell
Use the source URL in the JSON or CSV to inspect the current documentation. Check the operation direction, authentication, package scope, and publication status before changing a value. A successful HTTP response alone does not verify a capability.
Maintainers: update the JSON values, sources, and individual checked-on dates; set the overall date to the latest check. Run python3 scripts/growth/generate-agent-readiness.py, then python3 scripts/growth/generate-agent-readiness.py --check. Use --sources for the deduplicated URL checklist. Generation and validation are offline.
Corrections: alex@thunderphone.com. Dataset license: CC BY 4.0.