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

Annotations only declare readOnlyHint and openWorldHint, but the description adds substantial behavioral detail beyond that: seconds-level latency, incomplete worldwide coverage, no history retention, no key requirement, and a pay-per-successful-call pricing model via x402 on three chains with failures not charged. That is exactly the kind of context an agent cannot infer 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?

Two tightly packed sentences: the first defines the query and the payload, the second carries caveats and cost. No filler, and the coverage/price constraints are front-loaded where an agent will see them.

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 an output schema present, annotations covering safety, and full parameter documentation, the remaining burden is freshness, coverage, auth, and cost — all of which are stated explicitly. Nothing an agent needs to decide or call 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 description coverage is 100%, with each of the five parameters (north, south, west, east, limit) documented including ranges and defaults. The description's phrase 'lat/lon box' reinforces the spatial semantics but adds no bounds, ordering, or limit behavior beyond the schema, so the baseline 3 applies.

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 ('Live aircraft inside a lat/lon box from the public Flightradar24 feed') and enumerates the returned fields, so the agent knows exactly what it gets. It is clearly distinguishable from siblings like travel_flightaware_public_tracker or travel_google_flights without opening either 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?

The description supplies decision-relevant context — data is seconds old, coverage is not worldwide, there is no history and no API key — which implicitly tells the agent when not to use it (historical queries, exhaustive global coverage). It stops short of naming an alternative tool, so it does not reach a 5.

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