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

Annotations already declare readOnlyHint=true, so the description's read-only nature is not new. However, it adds meaningful behavioral context: 'Updates: annually' discloses data freshness, and the definition of the score (share of 242k airframes built before 1990) clarifies what the number represents. This exceeds the annotation baseline.

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 two sentences: the first delivers the core function and output fields, the second provides usage context and update frequency. Every sentence earns its place; no filler or redundancy.

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 simple read-only tool with no required parameters and no output schema, the description covers purpose, outputs (field names), usage triggers, and data cadence. The optional 'days' parameter is fully documented in the schema, so the lack of repetition is acceptable. The description is sufficiently complete for an agent to select and invoke correctly.

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% for the only parameter ('days'), which is fully specified. The tool description adds no parameter-level detail, so the baseline of 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?

The description opens with a specific verb ('Returns') and a precise resource: a '0-100 US general-aviation fleet obsolescence score' with listed output fields. This unique domain (GA fleet age, retrofit demand) clearly distinguishes it from the many sibling tools.

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?

Explicit when-to-use guidance is provided: 'Call when the user asks about GA fleet age, avionics retrofit or aircraft replacement demand, or aviation aftermarket sizing, or when timing MRO capacity, retrofit product-line, or parts-inventory investments.' This enumerates clear contexts, but no exclusions or alternative tools are named, stopping short of a 5.

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