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

The description goes beyond the readOnlyHint annotation by detailing credit costs: '1 base; hostMedia=true adds +2 per hosted asset (up to 24 / 49 max). Failed assets are not surcharged.' This provides operational context such as cost implications and limits, which is valuable for an agent managing budgets.

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?

The description is concise with two sentences: first states purpose and input, second lists credit costs. It front-loads the core purpose, then provides essential operational details without redundancy.

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?

The description covers the tool's purpose, input, and costing, but lacks details about the response structure or error handling. Since there is no output schema, an agent might need to infer the return format. However, for a list tool with clear parameters and read-only annotation, this is a minor gap; a mention of pagination or response fields would improve completeness.

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 all parameters are documented. The description adds cost and limit semantics for hostMedia ('adds +2 per hosted asset'), enriching its meaning beyond the schema's 'hosts source media for 90 days' with actionable pricing details.

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 clearly states it 'List Reels from a Facebook profile or Page,' specifying the verb, resource, and content type. This distinguishes it from sibling tools like facebook_profile_posts_list or facebook_profile_photos_list which target different content types.

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?

No explicit guidance on when to use this tool versus alternatives. It does not name facebook_profile_posts_list or instagram_profile_reels_list as alternatives, nor does it state conditions for choosing one over the other. The context is implied by the name but not articulated.

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