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

With only destructiveHint=false available, the description carries the load and does so well: it discloses the PUT-URL handoff, that raw bytes must be sent with the same MCP credentials, that the server validates size, SHA-256 and format before persisting, and that the file is kept private. These are non-obvious behaviors an agent could not infer from annotations or schema.

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 scope and the 'does not submit' boundary, then the mechanics; every clause carries information. It is dense and semicolon-chained, so a reader must parse carefully, but there is no filler.

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?

Six required parameters, no output schema, yet the description still explains the return value (dedicated PUT URL) and the post-upload lifecycle with submit_signup, which is what an agent needs. Missing details on URL expiry and whether the prepared entry can be re-prepared or overwritten.

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 50% and the description compensates: it explains that key identifies a specific signup file question, that key substitution is a rejected bypass, and that the SHA-256/size are validated against real bytes. It does not explain slug or fileName semantics, leaving part of the gap open.

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+resource (prepare upload for a designated signup file question) and immediately bounds it: 'does not publish the file, does not submit the signup'. This clearly separates it from sibling prepare_*_upload tools (activity material, activity photo) and from submit_signup.

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 an explicit gating condition ('only when the user supplies a real file'), an explicit exclusion (sensitive ID-type questions are rejected), a prohibition ('must not swap key to bypass'), and a downstream routing note that submit_signup reuses the saved attachment.

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