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

Annotations already declare readOnlyHint=true, openWorldHint=true and destructiveHint=false, so the safety profile is covered. The description adds genuinely new behavioral context not present in the annotations: per-page billing at $0.008 and the fact that pages are billed per fetched page. It does not cover pagination or rate limits, so it stops short of a 5.

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, zero filler, with the core action and identifier front-loaded before the return and cost details. Every sentence contributes something distinct.

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 carries the return-value burden and does so briefly ('reel metadata and engagement metrics'), and all parameters are documented via the schema. The picture is adequate, though a note on result volume/pagination would close the remaining gap.

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 schema already documents all three parameters including the billing note on 'pages' and the sentiment surcharge on 'get_sentiment'. The description's only parameter-adjacent detail (the id origin) is already echoed in the schema, so it adds little beyond the baseline.

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 states a specific verb and resource ('Get reels from a Facebook page') and names the required identifier and its source endpoint, so an agent knows exactly what is produced. It does not explicitly contrast itself with nearby siblings such as facebook_page_videos or facebook_page_posts, so it falls short of a full 5.

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?

The parenthetical '(from facebook_page_details)' implies a prerequisite lookup step, which is useful routing context. However, there is no explicit when-to-use/when-not statement and no named alternative (e.g., use facebook_page_videos for non-reel video content), leaving usage implied rather than stated.

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