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

Annotations already signal readOnly, idempotent, open-world, and non-destructive behavior, so the description does not need to restate safety. The description adds useful context beyond annotations: the data source, MIT license, no-auth requirement, and a detailed list of returned fields with ATC callsign examples. No contradiction with annotations is present.

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?

The description is well-structured and front-loaded with examples, then return information, then use cases, then source/license details. It is slightly redundant with the schema's parameter examples, but the extra context about use cases and external data source is valuable. Overall it is appropriately concise for the tool's simple one-parameter interface.

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, the description is complete: it explains what codes are accepted, what data is returned, why the tool is useful, and important operational details like no-auth and MIT license. The output schema is present, so the agent has full access to expected return values without needing the description to enumerate them further.

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?

The input schema has 100% coverage and already documents the code parameter, accepted code formats, examples, and the preference for ICAO codes. The description largely repeats this information rather than adding new parameter-level meaning. It includes examples like 'BAW' and 'BA', but these are also present in the schema, so the description provides minimal incremental value.

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?

The description clearly states a specific verb, resource, and action: 'Look up airline details by ICAO 3-letter code or IATA 2-letter code.' It also clarifies what is returned, making the tool's purpose immediately understandable. However, it does not explicitly differentiate itself from sibling tools like adsbdb.callsign.lookup, despite mentioning the word 'callsign' in the return fields.

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 provides a clear usage context: 'Useful for decoding transponder callsigns and identifying aircraft operators.' This gives the agent a practical sense of when to choose this tool. It does not explicitly state when not to use it or mention alternatives like adsbdb.callsign.lookup, so it stops short of full exclusion guidance.

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