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

Annotations already cover read-only, idempotent, and closed-world behavior, so the description's job is lighter. It adds genuinely useful context beyond the annotations: the results come from a cross-reference graph with a stated corpus size and a measurement date (2026-10-18), signaling a dated snapshot that may not reflect the latest data.

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?

A single front-loaded sentence with zero filler. The core action comes first and the supporting corpus statistics are parenthetical.

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 lookup with complete parameter schema and safety annotations, most needs are met. However, there is no output schema and the description does not indicate the return shape (e.g., list of part numbers vs. structured cross-references) or what happens when no substitutes exist, leaving a gap the agent must discover at call time.

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?

Only one parameter and schema coverage is 100%, with the schema itself describing 'Part number to find substitutes for'. Per the baseline rule for a single fully-documented parameter, no additional description text is required.

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 ('Find') and resource ('substitute / equivalent / cross-referenced part numbers') plus the data source (PartsTable cross-reference graph). It is clear what the tool does, but it does not explicitly distinguish itself from siblings like get-part or search-parts.

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?

No guidance on when to use this versus get-part, search-parts, or normalize-pn, and no note on whether the part number should be normalized first. The synonym list ('substitute / equivalent / cross-referenced') is the only hint at matching scope.

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