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

Annotations already establish readOnly, idempotent, non-destructive behavior, so the bar is lower. The description adds meaningful context beyond annotations: it discloses the data source (ADS-B DB), the license (MIT), that no auth is required, and that photo URLs are returned 'when available'. This is exactly the kind of supplement the dimension rewards, with no contradictions.

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?

Three sentences with zero waste. The action and primary inputs are front-loaded, the return fields are compactly listed, and the final sentence supplies identifier-format nuance plus source/license/auth context. Every clause earns its place.

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 a rich input schema, safety annotations, and an output schema, the description covers everything needed: accepted inputs, return values, data source, licensing, and auth status. No operational details like rate limits or pagination are essential here.

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 schema already documents the single `identifier` parameter with 100% coverage, including both formats, examples, and definitions. The description adds only marginal extra meaning, such as national registration prefix patterns (N-prefix for US, G- for UK), but most of its identifier explanation overlaps with the schema. Baseline 3 is appropriate given the high schema coverage.

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 states a specific verb ('Look up'), resource ('aircraft details'), and the two accepted input forms (Mode-S hex code or ICAO registration). It lists the exact data returned, making the tool's job unmistakable. It doesn't explicitly contrast with sibling tools like adsbdb.airline.lookup, but the aircraft focus is far clearer than typical definitions.

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 when to use it by thoroughly explaining both accepted identifier formats and giving concrete examples, but it never explicitly says when to choose this over the sibling adsbdb.airline.lookup or adsbdb.callsign.lookup. There are no exclusions or alternative routing cues, so an agent has to infer usage from the resource type alone.

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