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

Annotations already establish read-only, idempotent, non-destructive behavior, lowering the bar. The description adds genuine context beyond that: 'Individuals are not named' discloses a privacy redaction the agent should expect, and the PR-/PT- mark reservation explanation clarifies how the Brazil cross-registry result should be interpreted. No contradiction with annotations.

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?

Core scope is front-loaded and the privacy note is tersely effective. However, the description is a single dense run-on passage where the enumerated return fields partly duplicate what the output schema already provides, and the Brazil link sentence could be split for readability. Light restructuring would earn the top score.

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 one-parameter read-only lookup with an output schema and strong annotations, the description is largely complete: it covers scope, the distinctive cross-registry feature, and the privacy redaction. The main gaps are lack of sibling differentiation and no data-freshness caveat for FAA registry data, both minor at this complexity level.

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?

Parameter schema coverage is 100%, and the schema already documents that registration accepts an N-number with or without the leading N (N123AB, 123AB). The description only confirms the parameter is the key into the FAA registry, adding little beyond the schema. Baseline 3 is appropriate since the schema carries the semantic weight.

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 identifies a specific resource — 'US-registered aircraft (FAA registry) by N-number' — and enumerates the returned fields (status, model, year, airworthiness date, registrant type, base city/state, ICAO24 hex). The FAA-only scope and N-number key distinguish it from siblings such as jt_aircraft_lookup and jt_aircraft_lookup_batch, and the Brazil cross-registry link adds a distinctive capability.

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 implies the tool is for US FAA registry data keyed by N-number, and the Brazil link note gives the agent a sense of the tool's unique value. However, it never explicitly says when to prefer this over overlapping siblings like jt_aircraft_lookup, jt_aircraft_lookup_batch, or jt_cross_registry, nor does it state exclusions for non-US registrations.

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