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

Annotations already declare readOnlyHint, openWorldHint and destructiveHint=false, so safety is covered. The description adds genuinely useful context beyond that: what is returned (post text, author, engagement metrics, media) and the per-page pricing of $0.008, which matters for a paged, billable endpoint.

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 sentences, each earning its place: purpose and ID source first, then return contents, then sorting and cost. Nothing is padded and the most important routing information 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?

With no output schema, the description compensates by enumerating what is returned, and it covers the input prerequisite, sorting choice and billing model. An agent has everything needed to invoke it correctly.

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%, including enums, defaults and the per-page billing note for 'pages', so the schema carries the parameter burden. The description adds little parameter-level detail beyond restating sort options and the page-based billing already documented in the schema.

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 ('Get posts from a public Facebook group') with the key scoping detail that the group must be public and identified by numeric ID. It distinguishes itself from facebook_group_details by naming it as the source of the ID, and the 'group' vs 'page' framing separates it from facebook_page_posts.

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?

Gives clear prerequisites: the group must be public and the group_id must be numeric, sourced from facebook_group_details. It also documents sort options and billing behavior, but never states when to use this versus search_facebook_posts or how it differs from facebook_page_posts.

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