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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, so the safety profile is covered. The description adds useful behavioral context: it returns a canonical, singular ProductTwin and includes source-level provenance, which tells the agent the response carries traceability beyond basic fields. 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?

A single, front-loaded sentence communicates the core behavior, the resource type, and the provenance aspect without filler. It avoids repeating annotation information and earns every word.

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 operation with rich annotations and an output schema, the description is nearly complete. The main missing piece is guidance for when the agent lacks a stable identifier and should use sibling search tools, but that gap is already reflected in usage_guidelines.

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 0%, so the description must compensate for the single `id` parameter. It does so meaningfully by calling it a 'stable identifier', clarifying that it is a durable canonical key rather than an arbitrary name or label. The schema's pattern covers format constraints, so together they are adequate.

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 ('Returns'), a specific resource ('canonical ProductTwin'), and a distinguishing feature ('source-level provenance by stable identifier'). This clearly separates it from sibling search/list tools like search_candidates and 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 explicit when-to-use or when-not-to-use guidance is provided. The phrase 'by stable identifier' implies the caller already has the identifier, but there is no direction to use search-oriented siblings when the identifier is unknown, and no mention of error or not-found behavior.

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