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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is covered. The description adds genuinely useful context beyond them: it is keyless (no auth), it enumerates the returned data fields, and it clarifies that the document links are links rather than extracted text.

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?

Front-loads the core purpose, then the returned payload, then the sibling exclusion, then an example, then the keyless note. Every clause carries information an agent needs; nothing is padding.

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?

No output schema exists, so the description carries the return-value burden — and it does, enumerating ingredients, excipients, ATC codes, form, routes, prescription status, dates and document links. With annotations covering safety and the single parameter fully documented, nothing material is missing.

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%, so the baseline is 3, but the description adds meaning the schema does not: nregistro is defined as the Spanish national registration number and its provenance (cima_search_medicines) plus a concrete example call. It stops short of format/validation details, so not a 5.

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+resource (retrieve the full AEMPS CIMA record for one Spanish-authorised medicine) and pins the key to nregistro, including where that value comes from. It also explicitly distinguishes itself from cima_medicine_document_sections, so an agent can route between them 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 an explicit when-to-use boundary: use this for the record/links, use cima_medicine_document_sections for the actual document TEXT. It also tells the agent where nregistro originates (cima_search_medicines), covering the prerequisite for invoking it.

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