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text-to-speech

Text-to-Speech MCP Server

An MCP server that exposes a text-to-speech tool, powered by the free, no-API-key gTTS library (which wraps Google Translate's internal TTS endpoint).

  • Free — no API key, no billing, no GCP account.

  • Many languages — English, Bengali, Spanish, and ~60 more.

  • File output — saves an MP3 and returns its path.

  • Resilient — retries transient/rate-limit failures with exponential backoff.

Note: gTTS uses an undocumented Google endpoint. It requires internet access and can rate-limit or change without notice — great for personal/internal use, less suited to high-volume production. The engine is isolated in engine.py so it can be swapped for Google Cloud TTS or an offline engine later.

Requirements

  • uv

  • Python 3.12 (uv will provision it)

Related MCP server: mcp-tts-server

Setup

uv sync

This creates .venv/ and installs the project (and its deps: gtts, mcp).

Optional configuration — copy .env.example to .env and edit:

Variable

Default

Meaning

TTS_OUTPUT_DIR

./output

Where MP3s are written when no output_path is given

TTS_MAX_RETRIES

3

Max synthesis attempts before failing

TTS_RETRY_BACKOFF

1.0

Base backoff seconds (1s, 2s, 4s, …)

TTS_DEFAULT_LANG

en

Default language code

TTS_DEFAULT_ACCENT

com

Default accent TLD

Run

uv run tts-server
# or
uv run python -m tts_server.server

The server speaks MCP over stdio.

Tools

text_to_speech

Arg

Type

Default

Description

text

string

— (required)

Text to speak

language

string

en

Language code (en, bn, es, …)

slow

boolean

false

Speak more slowly

accent

string

com

Accent TLD: com (US), co.uk (UK), com.au (AU), co.in (India)

output_path

string

auto

Output MP3 path; auto-generated under TTS_OUTPUT_DIR if omitted

Returns: Saved <N> KB MP3 to <path>, or Error: <reason>.

list_languages

No arguments. Returns supported code: name pairs.

Install in an MCP client

This is a standard stdio MCP server, so it works with any MCP-compatible client (Claude Code, Claude Desktop, Cursor, Windsurf, Continue, etc.). Every client needs the same three things:

Field

Value

command

uv

args

["--directory", "<ABS_PROJECT_PATH>", "run", "tts-server"]

env (optional)

e.g. { "TTS_OUTPUT_DIR": "<ABS_OUTPUT_PATH>" }

Replace <ABS_PROJECT_PATH> with the absolute path to this project. Using uv --directory <path> run means the client can launch the server from anywhere and still resolve the right virtual env and .env. Make sure uv is on the client's PATH (or use the absolute path to the uv binary — find it with which uv).

Claude Code (CLI)

# user scope = available in every project; use --scope project for just this repo
claude mcp add text-to-speech --scope user -- \
  uv --directory /abs/path/to/text-to-speech-agent run tts-server

Verify, inspect, or remove:

claude mcp list                 # health check
claude mcp get text-to-speech   # show config
claude mcp remove text-to-speech

Tools load when a session starts, so open a new session after adding.

Claude Desktop

Edit the config file (Settings → Developer → Edit Config, or directly):

  • macOS: ~/Library/Application Support/Claude/claude_desktop_config.json

  • Windows: %APPDATA%\Claude\claude_desktop_config.json

Add (see claude_desktop_config.example.json):

{
  "mcpServers": {
    "text-to-speech": {
      "command": "uv",
      "args": ["--directory", "/abs/path/to/text-to-speech-agent", "run", "tts-server"],
      "env": { "TTS_OUTPUT_DIR": "/abs/path/to/text-to-speech-agent/output" }
    }
  }
}

Then fully restart Claude Desktop.

Cursor / Windsurf / other JSON-config clients

These use the same mcpServers JSON shape as Claude Desktop. Add the block above to the client's MCP config (e.g. Cursor: Settings → MCP, or ~/.cursor/mcp.json), then reload the client.

Generic stdio client

Any client that can launch a stdio server: configure it to run

uv --directory /abs/path/to/text-to-speech-agent run tts-server

and (optionally) pass environment variables from the table in Setup.

Troubleshooting

  • Server fails to start / "uv not found" — use the absolute path to uv (which uv) as the command, since GUI clients often don't inherit your shell PATH.

  • Tools don't appear — restart the client (Claude Code: start a new session).

  • MP3s land in the wrong place — set TTS_OUTPUT_DIR in the client's env block (it overrides .env).

  • Synthesis errors — gTTS needs internet and may rate-limit; the server retries automatically, but check connectivity if it persists.

Project layout

src/tts_server/
  server.py   # MCP tools, validation, response shaping
  engine.py   # gTTS wrapper + retry/backoff (only file importing gTTS)
  config.py   # env-driven settings
  utils.py    # filename gen, language validation, file sizing
tests/        # unit tests (retry paths, mocked gTTS)
output/       # generated MP3s

Tests

uv run python -m pytest -q

Available Tools

2 tools
list_languagesA

List the language codes and names supported for text_to_speech.

ParametersJSON Schema
NameRequiredDescriptionDefault

No parameters

Output Schema

ParametersJSON Schema
NameRequiredDescription
resultYes

TDQS

A3.9/5.0
Behavior2/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations provided, the description carries the full burden of behavioral disclosure. It only states that it lists supported codes and names, but does not disclose any behavioral traits such as authentication needs, rate limits, or idempotency. For a simple read-only list, the description is adequate but lacks depth.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a single concise sentence that is front-loaded and contains no wasted words. Every word is necessary.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given zero parameters and the existence of an output schema, the description is complete enough for an agent to understand and use the tool correctly. The sibling tool name provides context for when to call this tool.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

There are 0 parameters, and schema coverage is 100%. The description adds meaning by specifying that the output includes language codes and names, which is not evident from the empty schema. This provides useful context beyond the schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool lists language codes and names for text_to_speech. It uses a specific verb (list) and resource, and distinguishes from the sibling tool text_to_speech which performs speech synthesis.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description implies the tool is used to get supported languages before using text_to_speech, but it does not explicitly state when to use it or provide alternatives or exclusions. The context signals include a sibling tool name, which hints at the connection, but no explicit guidance.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

text_to_speechA

Convert text into spoken audio (MP3) using Google TTS (gTTS).

Args:
    text: The text to speak. Required, must be non-empty.
    language: Language code such as "en", "bn", "es". Defaults to "en".
    slow: Speak more slowly when True.
    accent: Google domain TLD controlling accent for some languages,
        e.g. "com" (US), "co.uk" (UK), "com.au" (AU), "co.in" (India).
    output_path: Where to write the MP3. If omitted, a timestamped file
        is created under the configured output directory.

Returns:
    A human-readable status string including the saved file path, or an
    "Error: ..." message describing what went wrong.
ParametersJSON Schema
NameRequiredDescriptionDefault
slowNo
textYes
accentNocom
languageNoen
output_pathNo

Output Schema

ParametersJSON Schema
NameRequiredDescription
resultYes

TDQS

A4.4/5.0
Behavior3/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

No annotations are provided, so the description must carry the burden. It explains the conversion process, parameter effects, and return format. However, it omits details like network dependencies, file overwriting behavior, or authentication needs, which are relevant for a tool using an external service.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is concise with a clear lead sentence, followed by well-organized Args and Returns sections. Every sentence adds value with no redundancy.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool's complexity (5 parameters, no schema descriptions, no annotations), the description covers all parameters and the return value comprehensively. The presence of an output schema is noted, and the description aligns with it.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters5/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 0%, but the description compensates fully by explaining each parameter (required, defaults, examples, behavior). It adds significant meaning beyond the bare schema types and names.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool converts text to spoken audio (MP3) using gTTS, with a specific verb ('Convert') and resource ('text into spoken audio'). It distinguishes from the sibling tool 'list_languages' by its action and output format.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The context of siblings (list_languages) implies this tool is for speech generation, not language listing. However, no explicit when-to-use or when-not-to-use guidance is provided, leaving some ambiguity.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

Tool Schema Changelog

Recent tool additions, removals, and schema changes observed during successful MCP inspections.

  1. 2 tool updatesv0.1.0
    • First observedlist_languages
    • First observedtext_to_speech

TDQS

A4.2/5.0

Scored across 2 tools

Disambiguation5/5

The two tools have clearly distinct purposes: one lists supported languages, and the other converts text to speech. There is no overlap or ambiguity.

Naming Consistency5/5

Both tools follow a consistent verb_noun pattern (list_languages, text_to_speech), making the naming predictable and intuitive.

Tool Count3/5

With only two tools, the server is quite thin but still covers the core functionality for a simple text-to-speech service. The count is borderline for the domain.

Completeness4/5

The domain is well-covered by listing languages and converting text to speech with various options. No major gaps are apparent, though additional settings tools could be added.

Maintenance

ActivityInactive
ResponsivenessNo issues

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