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

Annotations declare readOnlyHint=false, openWorldHint=true and destructiveHint=false, so safety is already covered; the description usefully adds that the result is a temporary link and that the file arrives as a host reference. It does not say that relaying stores a hosted copy, who can access the link, or that the link expires per ttl_hours, which are the meaningful behavioral facts beyond the annotations.

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?

One sentence, front-loaded with the platform restriction, then the action and the return value. Nothing is redundant and no sentence fails to earn its place.

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?

The nested file object is conceptually explained and the return is described as a temporary link, which is the key fact in the absence of an output schema. However, a non-read-only, open-world tool that materializes a shareable copy should also say where the copy lives and that expiry is governed by ttl_hours.

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%, including a documented ttl_hours range and default, so the schema carries parameter meaning. The description only clarifies the origin of the 'file' object (host-provided reference) and adds nothing about ttl_hours or the filename override, so the baseline 3 applies.

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 ('relay a file from the conversation') plus the concrete outcome ('get a temporary download link'), which is clearly distinct from the upload/read siblings. It stops short of naming an actual sibling, so the differentiation is inferable rather than explicit.

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?

'ChatGPT only' is an explicit applicability constraint, and 'the host passes it as a file reference' tells the agent exactly what input context must exist. No when-not conditions or alternative tools are given, but the positive context is unusually clear for a gateway-style tool.

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