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

Annotations already declare readOnly, idempotent, and non-destructive behavior. The description adds useful context such as returning a 'best-effort live price' and the correct iso.org page, and emphasizes reliability ('resolves any standard via its catalogue id'), going beyond what annotations provide.

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 three sentences long, front-loads the core purpose, and every sentence adds value without redundancy. It is efficient and well-structured.

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?

Given the tool's simplicity (one optional parameter, read-only, idempotent), the description covers all necessary aspects: what fields are returned, how to input the standard, and note on reliability. No output schema exists, but the listed fields are sufficient for understanding the return value.

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 fully describes the 'number' parameter, and the description enhances it by listing valid input formats (e.g., 'ISO-9001', 'ISO 9001:2015') and mentioning that 'reference' is an accepted alias, adding practical guidance beyond schema documentation.

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 clearly identifies the tool as retrieving a full record for a single ISO standard, listing specific fields returned (title, abstract, status, etc.) and distinguishing it from sibling 'search_standards' which would be for multiple results.

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 provides clear context for when to use the tool (to get detailed information for a known standard), but does not explicitly mention alternatives like search_standards when the standard number is unknown. The hint to use 'the reliable lookup' is helpful.

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