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

Annotations already convey that this is a mutating, non-destructive operation. The description adds meaningful caveats: chat attachments are not auto-injected, file/file_url must not be fabricated, and media should be pre-imported before attaching. This goes beyond the structured annotations without contradicting them.

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?

Three short, purposeful sentences provide the core action, the preferred workflow, and the important caveat. The most important information is front-loaded and there is no redundant summary or 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?

With 100% schema coverage and clear description-level guidance, the tool is fully comprehensible. The description covers the target post state, the input modes, the option hierarchy, and the critical automatic-injection ambiguity an agent might otherwise assume.

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 is 3. The description adds value by explaining the preferred workflow across parameters: prefer asset_ids for existing media, import external media first, and treat file/file_url as supply-conditional rather than default inputs.

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 leads with a specific verb-object pair: attach media to the authenticated user's DRAFT. It clearly targets the draft post and distinguishes the tool from siblings like detach_assets_from_post and import_media_from_url by framing it as an attachment action.

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 actionable selection guidance: prefer existing asset_ids, import fresh external media first and use the returned Asset ID, and only use file/file_url when the client actually supplies them. It does not explicitly name alternative tools or spell out when not to use it, but the usage context is clear.

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