Upload message attachment

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

Goes well past the annotations: ~90-day lifetime, Page-only scope, no delivery to recipients, dry-run-by-default with apply:true. The only gap is that idempotentHint=false is not addressed — it never says whether re-uploading the same URL yields a new attachment_id or dedupes, which matters given the "without a re-fetch" framing.

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 action and the payoff, and every clause carries information (scope, lifetime, consumer, delivery, dry run). It is a single dense run-on sentence with em-dash asides, which slightly hurts scanability but wastes nothing.

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 5-parameter write tool with 100% schema coverage and no output schema, the description supplies the full picture: what is written, where, for how long, who it is visible to, how to activate it, and what the returned id is for. Nothing an agent needs to call it correctly is missing.

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 3 is the baseline; the description still adds real meaning by tying the returned id to send_message, naming the dry-run/apply contract, and scoping the id to one Page for ~90 days. The url size/timeout limits and type enum are left entirely to the schema, which already covers them well.

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 ("Upload ONE file ... to the Page's Messenger attachment store") plus the artifact produced ("reusable attachment_id") and its consumer (facebook_send_message). This clearly separates it from every other sibling, none of which touch the attachment store.

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?

Explicitly frames the tool as a pre-step whose output feeds facebook_send_message as attachment.attachment_id, and rules out the wrong expectation with "Nobody receives anything." The dry-run default and apply:true switch are stated inline, so the agent knows the activation condition without opening the schema.

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