UnlimitedTTS for Agents

Non-custodial, quote-first text-to-speech for AI agents:

• @unlimitedtts/core validates live x402 challenges, enforces spend policy, persists sanitized receipts, and writes private MP3 artifacts.

• @unlimitedtts/mcp exposes tts_list_voices, tts_quote, and irreversible tts_synthesize tools over stdio.

• @unlimitedtts/openclaw bundles the MCP server and the unlimitedtts agent skill.

• skills/unlimitedtts supports MCP-guided and direct wallet-aware HTTP workflows.

The implemented v1 path is external-signature mode. A separate wallet tool creates the x402 v2 PAYMENT-SIGNATURE; this code never accepts a seed phrase or private key.

Install and build

Node.js 20 or newer and pnpm are required.

pnpm install --frozen-lockfile
pnpm check

Run the local server from this checkout:

pnpm --filter @unlimitedtts/mcp build
node packages/mcp/dist/cli.js

Generic MCP configuration after npm publication:

{
  "mcpServers": {
    "unlimitedtts": {
      "command": "npx",
      "args": ["-y", "@unlimitedtts/mcp@0.1.0"],
      "env": {
        "UNLIMITEDTTS_MAX_USDC_PER_CALL": "0.10",
        "UNLIMITEDTTS_ROLLING_24H_USDC": "1.00",
        "UNLIMITEDTTS_OUTPUT_DIRECTORY": "/absolute/approved/output"
      }
    }
  }
}

OpenClaw local development:

pnpm --filter @unlimitedtts/openclaw build
openclaw plugins install -l ./packages/openclaw
openclaw plugins enable unlimitedtts
openclaw gateway restart
openclaw plugins inspect unlimitedtts --runtime --json
openclaw plugins doctor

Related MCP server: mcp-ai-voice

Payment flow

1. tts_list_voices retrieves /docs and /tts/voices and caches the result for five minutes.

2. tts_quote sends the exact synthesis body to /x402/tts without payment, validates the returned PAYMENT-REQUIRED, enforces local policy, reserves rolling budget, and returns a short-lived HMAC token.

3. A wallet signs only the returned selectedRequirement.

4. tts_synthesize verifies the token, unchanged body hash, complete x402 v2 accepted entry, exact-EVM payee and value, then sends one paid retry.

5. A successful call requires both audio/mpeg and PAYMENT-RESPONSE. It commits the budget, writes a sanitized receipt, atomically stores the MP3 with mode 0600, and returns structured metadata plus MCP audio/resource content.

PAYMENT_OUTCOME_UNKNOWN permanently quarantines that quote in the local ledger. The server never automatically submits or authorizes a second payment.

Configuration

Payee rotation must be released through trusted configuration. The server never learns an allowed payee from an untrusted challenge.

Production remains the default and is pinned to Base mainnet. For staging validation, set UNLIMITEDTTS_ENVIRONMENT=staging; this selects https://staging-api.unlimitedtts.com, Base Sepolia (eip155:84532), and staging USDC. The core rejects the staging origin, network, or asset when the environment is not explicitly staging.

Scope

This checkout implements the portable local MCP, external wallet adapter contract, agent skill, OpenClaw package, tests, and registry metadata. Hosted Streamable HTTP, temporary R2 storage, prepaid-card synthesis, and a concrete managed automatic signer are intentionally not advertised as completed v1 features.

See required and recommended upstream changes before enabling unattended automatic signing or a hosted service.