transcribe_url

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

Annotations already declare readOnlyHint=false, openWorldHint=true, idempotentHint=false, destructiveHint=false, so the safety profile is covered. The description nevertheless adds substantial context beyond them: per-call cost of 0.25 USDC via x402 on Base, the AGENT_PRIVATE_KEY requirement, the MAX_USDC_PER_CALL guardrail, 25 MB / 30 minute caps, and SHA-256 binding of outputs — though it doesn't explain whether identical URLs produce identical results given the non-idempotent hint.

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?

Front-loaded with the purpose and outputs, then limits, then exclusions, then cost — a sensible ordering. It repeats itself somewhat ('Transcribe an audio or video file URL' immediately followed by 'Transcribes a public audio or video FILE URL'), costing a little tightness.

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 carries the return-value burden and does so: timestamped segments, SRT, VTT, plain text, bound to the media hash. Cost, auth, size and duration limits are all present, leaving nothing an agent needs before calling.

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%, so baseline is 3, but the description adds a constraint not present in the schema — the 25 MB file-size cap — and clarifies the media-type boundary of the url parameter beyond its bare pattern. It does not elaborate on formats or language semantics, which the schema already handles.

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?

States a specific verb and resource (transcribe an audio/video file URL) plus the engine, output formats, and limits. No sibling tool in the list does transcription, so differentiation is trivially satisfied and the scope is unmistakable.

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?

Gives explicit when-not guidance: no YouTube, Spotify, or streaming pages — the URL must be the media file itself, and speakers are not identified nor translated. It doesn't name an alternative tool to use instead for those rejected cases, but it's clear about the conditions under which this tool applies.

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