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

Goes well beyond readOnlyHint/openWorldHint: discloses that only the first server-rendered page is returned, that pagination.hasMore can be true with no cursor available to fetch more, that listing entries lack host and description, that ordering is Facebook's own ranking, and that each call costs 1 credit. These are exactly the operational constraints an agent needs before calling.

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?

Five tight sentences, front-loaded with what the tool returns, followed by filter semantics, page limits, and cost. No filler or repetition of 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?

For a read-only, no-output-schema listing endpoint, the description covers the meaningful unknowns: what the feed is, what fields are absent, pagination limits, ordering nondeterminism, and cost. An agent could invoke it correctly without further exploration.

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 coverage is 67%, and the description adds real meaning for `time` beyond the schema's 'Defaults to all upcoming' by explaining the resulting ordering and scope. It also restates the accepted `url` forms (Explore URL or bare slug/id pair). `cache_max_age` remains undocumented in both schema and description, keeping it below a 5.

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 with scope: 'Public events Facebook is suggesting for a city, from its Events Explore feed,' backed by a concrete example URL. The agent can tell this apart from facebook_event (detail view) because the description explicitly says host/description only exist on /v1/facebook/event.

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?

Explains when to use the `time` filter versus omitting it ('without it Facebook returns whatever it has queued as upcoming, in whatever order it ranks them') and routes the agent to the event-detail endpoint for host/description. It does not mention facebook_eventsSearch or facebook_profileEvents as alternatives for keyword or per-profile event lookups, so the sibling routing is incomplete.

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