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

Annotations already declare readOnly/openWorld/non-destructive, and the description adds value beyond them: the returned fields (names, IDs, links), the cost model ("Billed $0.008 per page"), and the fact that paging drives cost. It does not cover rate limits or result caps, but the billing disclosure is genuinely useful for an agent controlling call volume.

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 tight sentences: purpose, return shape, then refinement and cost. The primary verb is front-loaded and nothing is redundant with the title.

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 naming the returned fields, and it covers scoping, cost, and the upstream dependency for location_id. Minor gaps remain around pagination behavior and maximum result counts for a multi-page billed call.

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 baseline is 3, but the description adds semantics the schema lacks: start_date/end_date are framed as range limits and location_id is tied to its upstream source tool. It also links the pages parameter to billing, which the schema only mentions in isolation.

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?

Specific verb+resource ("Search public Facebook events by keyword") with the scope qualifier "public" made explicit. It is clearly distinguishable from the numerous search_facebook_* siblings (posts, pages, videos, locations) without opening any schema.

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 concrete narrowing strategies (limit by date range, scope by place) and names the upstream sibling search_facebook_locations as the source of location_id. It stops short of stating when this tool should be preferred over sibling searches like search_facebook_pages, but the context is clear enough to route correctly.

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