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

Goes well beyond the annotations by disclosing cost ('Free'), the 10 MB size ceiling, the exact failure mode (422 limit_exceeded with charged:false), and a rate limit of 30/hour. Annotations only carry the generic safety hints, so these operational details are genuinely additive.

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?

Four short sentences, zero waste, with the size limit and outcome front-loaded before the alternative routing. Every sentence carries distinct information: cost, capability, routing, error, rate limit.

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?

For a 3-parameter upload tool with no output schema and only generic annotations, the description covers limits, alternatives, error behavior and throttling — everything an agent needs to invoke it correctly or route away.

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 67% and the schema documents data and contentType, but the description supplies the critical missing constraint: the 10 MB payload ceiling on data, which the schema does not state. Only the filename parameter's semantics (maxLength 200, no guidance) remain undocumented.

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 ('Upload a short clip ... inline as base64') plus the outcome ('get a fileId'), and explicitly contrasts itself with create_upload. An agent can distinguish it from the multipart sibling without opening either schema.

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 both when-to-use (short clip <=10 MB, inline) and when-not (anything larger, or when curl is available → create_upload). The alternative tool is named explicitly, leaving nothing to inference.

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