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by io.github.magichourhq
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fetch_audio_download

Fetch a audio downloads[n].url from a completed audio project and return it as inline MCP audio content for compatible clients. Pass the exact full signed URL from downloads[n].url without trimming query parameters; expires_at is separate metadata, not part of the URL.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
contextNoExplain in 15-25 words, in third person, why this tool is called and how it supports the user's goal. For analytics only. You MUST describe only the abstract purpose of the tool call. NEVER include, repeat, paraphrase, or infer personal, sensitive, or identifying information from the user request or tool results, including names, emails, phone numbers, IPs, IDs, or credentials. You MUST generalize specific entities into roles such as "a user", "the customer", or "an account". Example: "Retrieving a customer's recent orders to investigate a billing issue and help support determine the appropriate resolution."
max_bytesNo
download_urlYes

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changed
    • addedInput schema / properties / context
      Added value: +{
+  "description": "Explain in 15-25 words, in third person, why this tool is called and how it supports the user's goal. For analytics only. You MUST describe only the abstract purpose of the tool call. NEVER include, repeat, paraphrase, or infer personal, sensitive, or identifying information from the user request or tool results, including names, emails, phone numbers, IPs, IDs, or credentials. You MUST generalize specific entities into roles such as \"a user\", \"the customer\", or \"an account\". Example: \"Retrieving a customer's recent orders to investigate a billing issue and help support determine the appropriate resolution.\"",
+  "type": "string"
+}
  2. First observed

TDQS

A4.2/5.0
Behavior4/5

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

No annotations are provided, so the description carries the full burden; it discloses that output is inline MCP audio content, that only compatible clients can consume it, and the critical gotcha that the signed URL must be passed verbatim with query parameters intact. It omits error/expiry behavior and how max_bytes constrains the response.

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?

Two tight sentences: the first states purpose and return type, the second front-loads the most common failure mode (URL trimming) plus the expires_at clarification. No filler, and the highest-value guidance comes early.

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

Completeness4/5

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

With no annotations and no output schema, the description correctly describes the return form (inline audio) and the key call-time pitfall. It is nearly complete but leaves the max_bytes size-limit behavior and any failure mode for expired/signed URLs unexplained.

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

Parameters3/5

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

Schema coverage is only 33% (only 'context' is documented), so the description must compensate. It does explain the required download_url semantics (exact full signed URL, do not trim query params) but says nothing about max_bytes, leaving one of three parameters undocumented in both places.

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?

States a specific verb ('Fetch') plus resource ('audio downloads[n].url from a completed audio project') and the resulting form ('inline MCP audio content'). The audio scoping cleanly distinguishes it from the parallel fetch_image_download and fetch_video_download siblings without needing the schema.

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?

Gives a clear prerequisite ('from a completed audio project') and a client constraint ('for compatible clients'), which tells the agent when the tool is applicable. It stops short of explicitly naming when to prefer a sibling or what to do if the project is not complete.

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

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