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

Annotations already declare readOnlyHint, destructiveHint=false, and idempotentHint, so the safety profile is largely covered; the description nonetheless adds specific behavioral detail by enumerating what it will never do ('never posts, messages or edits a Page') and noting the per-page ad-eligibility flag. It stops short of describing pagination or result size, which is minor given the annotation coverage.

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?

Two tight sentences: the first states the resource and its per-item attribute, the second gives the actionable trigger and the read-only guarantee. Nothing is repeated from the title and nothing is padding.

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 say the response enumerates pages plus ad-backing capability, which is enough to use it. It does not mention pagination or the relationship to a specific client/account scope, a small gap for a list tool in an agency context.

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?

There are zero input parameters, so the baseline is 4. The description still introduces the key field the agent will consume (page_id) and explains why it matters, which is useful framing even though no parameters need documenting.

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 ('List the Facebook Pages this agency can act for') plus the discriminating payload attribute ('whether each one can back an ad'). That resource is clearly distinct from the account-, campaign-, and insight-oriented siblings, so an agent can pick it without opening schemas.

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?

Explicitly says when to reach for it: 'A lead-gen or traffic ad set must name a Page, so use this to find the right page_id before building an ad.' That is a clear trigger, though it doesn't name an alternative tool (e.g. meta_list_accounts) or a when-not-to-use case.

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