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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so safety is covered. The description adds genuine value by enumerating the returned data, including custom properties and invoice usage, since there is no output schema. It says nothing about behavior when the ID is invalid or not found, which matters for a lookup tool.

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, front-loaded with the core action, then the return payload, then usage. The field enumeration earns its length because no output schema exists to carry that information, and there is no filler.

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 single-parameter read tool with rich annotations, this is nearly complete: it explains purpose, use cases, and return contents without an output schema. The remaining gap is undocumented failure behavior (unknown ID, permission issues) and no guidance on when to prefer a listing call instead.

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 coverage is 100% and the single id parameter is documented in the schema, including its provenance from list_products. The description only reiterates 'by ID' without adding format, validation, or error semantics beyond the schema, so the baseline 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?

States a specific verb and resource with scope: 'Fetch full details of a single product by ID', which cleanly separates it from list_products (all products) and from create/update/delete_product. It also enumerates the returned fields, so an agent knows exactly what it gets without opening a schema.

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?

Gives two concrete when-to-use conditions: before an update to get current state, and when a user asks about a specific product's details. It does not name an explicit alternative for bulk listing (e.g., list_products) or state a when-not, so it stops short of full routing guidance.

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