stream_compose
Stream Composed Music. Spends ElevenLabs credits. Returns audio/* bytes; pass output_path to save them.
This record as markdown: /tools/aiwerk-mcp-server-elevenlabs/stream-compose.md
What stream_compose does on Elevenlabs
AI agents use stream_compose to create or update resources in Elevenlabs, usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Elevenlabs environment.
| Parameter | Type | Required | Description |
|---|---|---|---|
seed | number | null | — | |
prompt | string | null | — | |
model_id | string | — | |
finetune_id | string | null | — | |
lyrics_text | string | null | — | |
output_path | string | — | Where to write the returned bytes. Relative paths resolve against ELEVENLABS_OUTPUT_DIR. Omit it to get the data inline as base64 (small files only). |
music_prompt | object | — | Composition plan for the `music_v1` model. Using this field with any other model will result in an error. |
output_format | string | — | Output format of the generated audio. Formatted as codec_sample_rate_bitrate. Use "auto" (the default) to let the API pick the best format for the selected mode |
generation_mode | object | — | |
music_length_ms | number | null | — | |
composition_plan | object | — | |
finetune_strength | number | — | How strongly the finetune influences the generation. Defaults to 1.0 (full strength). Lower values soften the influence of the finetune, leaving more room for p |
Parameters from the server's own tool schema.
Why stream_compose is rated Medium
An AI agent can call stream_compose faster than any human can review: one bad instruction and it creates or modifies resources in Elevenlabs by the hundred, each call as confident as the last.
Risk signalsHigh parameter count (15 properties)
Attacks that exploit this kind of access
The rule that runs stream_compose safely
PolicyLayer is an MCP gateway: it sits between your AI agents and Elevenlabs, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For stream_compose, this is the rule to start with:
stream_compose stays usable, but capped: an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.
The button opens the PolicyLayer dashboard: create your workspace, connect Elevenlabs, apply this rule, and every stream_compose call is checked against it from then on.
Questions about stream_compose
Stream Composed Music. Spends ElevenLabs credits. Returns audio/* bytes; pass output_path to save them. It is categorised as a Write tool in the Elevenlabs MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
stream_compose accepts 12 parameters: seed, prompt, model_id, finetune_id, lyrics_text, output_path, music_prompt, output_format, generation_mode, music_length_ms, composition_plan, finetune_strength. The full parameter table on this page comes from the server's own tool schema.
Register the Elevenlabs MCP server in PolicyLayer and add a rule for stream_compose: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Elevenlabs. Nothing to install.
stream_compose is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the stream_compose rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for stream_compose. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
stream_compose is provided by the Elevenlabs MCP server (@aiwerk/mcp-server-elevenlabs). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
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