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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the description's job is lighter. It still adds real behavior beyond them: results are ordered newest first, they come straight from Meta rather than a local store, and a 409 not_connected is returned when the channel isn't connected — an error contract the annotations cannot express.

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 what the tool returns and followed by the trigger-chaining note and the error case. Dense but each sentence carries information; no filler or restatement of the name.

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 no output schema, the description would ideally say something about the shape of returned posts and how to page using starting_after. It covers ordering, source, chaining and the main error, but leaves pagination behavior and the returned fields unaddressed for a three-parameter list tool.

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 description coverage is 100%, so limit (1-50, default 25), platform (instagram/facebook enum) and starting_after (Meta next_cursor) are already fully documented in the schema. The description adds no parameter-level meaning — it never mentions pagination or which platform default applies — 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?

The description gives a specific verb and resource ("List recent posts") and adds scope detail: Instagram or Facebook posts and Reels, newest first, sourced live from Meta. It does not, however, distinguish itself from the sibling list_posts, leaving the agent to infer the difference between a live recent fetch and whatever list_posts returns.

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?

There is implied usage (fetch recent content from the connected channel) plus a useful chaining hint that an id can be reused as post_id when creating a trigger scoped to one post. But it never states when to prefer this over list_posts or get_top_posts, and gives no exclusions, so the routing decision is left partly to inference.

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