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

Annotations already declare non-read-only, non-destructive, non-idempotent and closed-world, so the description's job is to add the non-obvious traits — and it does: the file is copied (the original can be moved or deleted afterwards), no media editing ever happens, and size/platform limits are deferred to post creation. It does not say whether re-adding the same path yields a new id, which matters given idempotentHint=false.

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, front-loaded with the action and the returned id, then formats, then lifecycle, then scope. Every sentence carries information an agent could act on; nothing is padding.

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 tool with full schema coverage and complete annotations, the description covers formats, copy semantics, and the deferral of limits, which is enough to call it correctly. Minor gaps remain around duplicate handling and the alt-text/org options, but they don't block correct invocation.

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 the baseline would be 3, but the description adds real meaning to the `path` parameter by enumerating accepted formats (JPEG, PNG, WebP, GIF, MP4, MOV) that the schema does not list. `alt` and `org` are left entirely to the schema text.

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 concrete verb plus resource ('Copy an image or video into Statuz') and even names the payoff ('get an id to attach'), so the agent knows exactly what the call produces. The line 'Statuz never edits media' implicitly separates it from media_edit, and the copy semantics separate it from media_list/media_remove.

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 phrase 'get an id to attach' places the tool in the create-post workflow, and 'platform limits are checked when a post is created' tells the agent this call will not validate platform constraints. There is no explicit when-not or named alternative (e.g. media_edit for changing alt text later), so it stops short of full routing guidance.

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