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

Annotations already establish readOnlyHint and openWorldHint, so the description need not restate safety. It adds material context beyond the annotations: the exact response contents and the credit cost ('Cost: 1 credit'), which is important for an agent budgeting calls. It doesn't cover rate limits or failure modes.

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

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

Three short sentences, zero filler: purpose first, return contents second, cost last. Every sentence carries information the agent needs.

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

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

With no output schema, the description compensates by naming the returned fields and the related reels, and it discloses cost. For a single-parameter read tool with annotations covering safety, nothing essential is missing.

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

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

Schema coverage is 100% for the single id parameter, so the baseline is 3. The description goes beyond the schema's 'Numeric audio id' by explaining provenance ('Audio ids come from reels'), which meaningfully helps an agent construct a valid call.

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

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

The description gives a specific verb+resource ('Get an Instagram audio track') and enumerates the returned fields (title, artist, duration, preview URL) plus the associated reels. It does not explicitly name the sibling instagram_audio_search as an alternative, so it stops short of the top score.

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

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

It supplies one genuinely useful usage hint: 'Audio ids come from reels,' telling the agent how to obtain the required id. However, it never says when to prefer this over instagram_audio_search or instagram_reels, which is the natural selection question for this tool.

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