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

Annotations already declare read-only, idempotent, non-destructive and open-world behavior, so the safety profile is covered. The description adds the accepted input grammar and a no-guessing constraint, but says nothing about failure behavior for non-numeric/vanity permalinks or what success looks like.

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?

Two tight sentences: the accepted forms come first, the exclusion and alternative second. No filler, no restatement of the tool 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?

For a resolution helper with no output schema, the description never says what 'verify' returns (a canonical post ID? a post object? just a boolean?). The account_id prerequisite is only in the schema. Adequate but leaves a real gap about the result an agent will get back.

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%, and the schema description for post_id_or_url already states 'numeric Facebook permalink with both author and post IDs'. The description restates the same permalink forms with example URL syntax, which is mildly helpful but does not go beyond the schema's meaning.

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 ('Verify a Facebook post ID or numeric permalink') and spells out the two accepted URL shapes. It differentiates itself from facebook_list_user_posts, though it does not clarify its relationship to the natural downstream sibling facebook_get_post, which an agent would likely pair it with.

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 routing is present: 'Other URLs require facebook_list_user_posts' names the alternative and the condition that selects it, and 'never infer missing IDs' gives a hard exclusion. It stops short of saying what to do after a successful resolution or how the tool relates to get_post.

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