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

Goes well past the annotations: one-time URL, 15-minute expiry, single-file scope, PUT with no auth header, byte-level format validation, plan-dependent size limit surfaced via max_bytes. The only gap is that it doesn't say what happens if the URL expires unused or whether uploads count against a quota.

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 the core outcome, then the mechanics, then the accepted formats and the public-URL exclusion. Dense but nearly every clause carries operational value; the parenthetical format list and curl snippet are the only parts that push 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?

No output schema exists, and the description compensates fully by naming the returned fields (upload_url, media_url, max_bytes) and how to use each. Combined with the delivery mechanics and format list, an agent has everything needed to call it and complete the upload.

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%, so both optional parameters are already documented in structured form; the description only loosely echoes them (filename 'used in the example command', size checked against the plan limit). Baseline 3 applies since the schema carries the parameter load.

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 ('this returns a one-time upload_url') for a clearly scoped job: attaching a local file. It also distinguishes itself from the post-creation siblings by naming where media_url gets consumed (create_post / schedule_post / queue_post / update_post).

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?

Explicit when-to-use ('a file from your machine'), explicit when-not ('Files already on a public URL don't need this: pass the URL directly'), and explicit next step for the returned media_url. Nothing about tool selection is left to inference.

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