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

Annotations only declare readOnly and openWorld; the description goes well beyond them by disclosing credit pricing, the extra-credit cost of extra_fetch with a refund clause on unreadable fetches, and the data-quality caveat that followerCount may be rounded to ±500,000 with raw.followerCountIsApproximate as the discriminator. That is exactly the kind of behavioral context an agent cannot get from structured fields.

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?

Front-loaded with what the tool returns, then the caveats and cost model; sentences carry information rather than filler. It is dense and slightly long, but nearly every clause (rounding, refund, credit cost) earns its place.

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 does the work of naming returned fields (including the raw.* sub-fields) and the cost/refund behavior, which is enough for an agent to call it correctly. The only real gap is cache_max_age, undocumented anywhere, which slightly weakens completeness for a 3-parameter tool.

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?

extra_fetch is explained in depth, including its cost model (1 extra credit per page, large additional fetch) and its effect on createdAt, adding real meaning beyond the schema's generic wording. url is only implied from 'Page URL, @handle, slug, or numeric page id', and cache_max_age is completely unaddressed in both schema and description, keeping this below 5 despite 67% coverage.

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 resource – a public Facebook Page profile – and enumerates the fields returned (name, category, follower/like counts, description, banner, outbound links), so the agent knows exactly what it gets. It doesn't explicitly contrast with siblings like facebook_pagePosts or facebook_profilePhotos, leaving that distinction to name inference.

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?

There is no statement of when to use this tool versus the many sibling facebook_* tools (pagePosts, pageAds, profileEvents). The only conditional guidance is parameter-level ('Pass extra_fetch=true to also fill createdAt'), which is invocation guidance rather than tool-selection guidance.

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