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

Annotations already declare read-only, open-world, non-destructive behavior, so the description need not cover safety. It goes further by disclosing per-action credit pricing, return sizes (3-9 posts per call), pagination via end_cursor, and timezone handling — genuinely useful operational context. It stops short of noting failure modes for private/inaccessible groups or any rate limits beyond pricing, keeping it out of 5 territory.

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?

One lead sentence plus a clean per-action bullet format that groups purpose, pricing, and inputs consistently, so the agent can scan to a single action. It is somewhat long and repeats 'Pricing: 1 credit per call' across actions, but no sentence is empty of content and the purpose is front-loaded.

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 six-action tool with an output schema, the description supplies everything an agent needs: what each action returns, which inputs it requires, the inter-action dependencies (id before albums, albums before album_items), and cross-tool links to facebook_page. Return-value details are covered by the output schema, so nothing essential 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 description coverage is 100%, so the baseline is 3, but the description adds real meaning: it maps each parameter to the actions that require it (link for details/id/posts/videos, group_id for albums, album_id for album_items) and explains that group_id comes from action=id and album_id from a prior albums call. The after_time/before_time date-filtering intent is also clarified beyond the bare ISO-8601 schema note.

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 opening line names a specific resource (public Facebook groups) and its scope (details, group ID, posts, videos, photo albums), then each action is spelled out with the exact data it returns. It clearly differentiates itself from siblings like facebook_page by explicitly noting that album_items works for both, and by restricting the domain to groups.

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?

Every action carries explicit routing guidance: 'Use action=posts for its posts', 'Use action=details for the group's data', and 'To get the photos in an album, pass its album_id to action=album_items'. Prerequisites are stated (albums needs the numeric group ID from action=id), so the agent knows the correct call sequence rather than guessing.

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