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

The description goes well beyond the annotations, explaining that bytes never pass through the API, the size is signed into the URL, there is no proxy, limits are 25 MB and 1-30 days retention, and keys are unguessable. It also documents pricing and auth requirements. This does not contradict the readOnlyHint because the tool itself only returns URLs; the agent performs the PUT.

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 description is longer than the minimum but every major clause adds value: mechanism, limits, use-case, required input, and pricing. It is front-loaded with the core purpose. Some phrasing like 'Somewhere to put the file' and 'The step every agent hits' is slightly redundant but not harmful.

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?

Given the output schema exists, return values need no explanation. The description covers required input, size limits, retention bounds, storage mechanics, pricing, auth model, and the concrete use case. An agent has everything needed to invoke this tool correctly and understand its behavior.

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 all parameters. The description adds useful emphasis on bytes ('Declare bytes= and the size is signed into the URL') and mentions retention limits, but it does not significantly deepen the meaning of name, ttlDays, or contentType beyond what the schema provides.

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 action and resource: 'Get a signed upload URL and a retrieval URL for one file, in one call.' It clearly distinguishes this from file_publish or file_convert by focusing on temporary storage for a newly produced file. The verb/resource pair is unambiguous.

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?

The description gives strong contextual guidance: 'The step every agent hits the moment it produces a report, chart, CSV or build and has nowhere to put it.' It clearly says when to use the tool, though it does not explicitly name alternatives or exclusion conditions.

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