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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered; the description adds genuine context by disclosing what comes back (flight, other airport, status, time) despite there being no output schema, plus 'Free, no key' which tells the agent no auth or billing setup is needed. It does not mention data freshness/lag or whether the airport identifier must be uppercase, which keeps it from a 5.

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?

One compact, front-loaded sentence plus two short qualifiers covering identifier formats and auth/cost. Every clause earns its place; no filler or restatement 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 single-parameter read-only lookup with no output schema and no annotated safety gaps, the description covers the identifier formats, the returned field set, the real-time nature of the data, and the absence of auth. Nothing an agent needs in order to call it correctly is missing.

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 0% and the sole 'airport' parameter is a bare string, so the description must carry the burden — and it does, specifying that either ICAO ('KJFK') or IATA ('JFK') identifiers are accepted, with concrete examples. That is meaningful disambiguation that the schema alone does not provide.

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 resource and scope ('Live departures and arrivals board for an airport') and enumerates the returned fields (flight, other airport, status, time), so an agent can distinguish it from flight_status or flight_on_date without opening the schema. It stops short of naming a sibling or stating the one-board-per-airport scope explicitly, so it is clear but not maximally differentiated.

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?

Usage is only implied: 'live' suggests current, real-time boards, contrasting with a historical tool like flight_history, but there is no explicit when-to-use or when-not-to-use statement and no named alternative. An agent must infer that this is for current airport boards rather than per-flight lookups.

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