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

The description goes well beyond the annotations: it discloses that no email is sent, that download links expire after 1 hour, that the server fetches from download_url and stages the file in R2 during the job, that processing runs in a headless browser, and that the input is deleted when the job ends. This is the kind of lifecycle and side-effect detail annotations cannot carry.

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?

The key correction ('does not send any email') is front-loaded, which is good. But the trailing detail about Cloudflare R2, headless browser, and ihateaudio.com is infrastructure trivia that does not help an agent decide or invoke the tool, padding the length.

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 helpfully covers the return value (download links) and their 1-hour expiry, plus the input constraint and lifecycle. It is close to complete for invocation; the main omission is explicit routing against the resizing siblings.

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 description coverage is 100%, so the schema already documents files, outputFormat and bitrateKbps. The description adds only a light qualifier that outputFormat/bitrate are honored 'where the tool supports them,' which marginally aids the agent. Baseline 3 is appropriate.

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 states a specific job: recompress or split audio to fit email attachment limits, and explicitly clarifies that it returns files rather than sending email. This resolves the apparent mismatch with its name. It stops short of naming the closest functional siblings (audio_compressor, audio_splitter) that also resize audio.

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?

Usage is implied by the email-attachment-limit framing and the stated input requirement (a file with a public HTTPS download_url). However, it never states when to choose this over sibling tools like audio_compressor or audio_splitter, nor any exclusions. Adequate but clearly gapped.

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