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

With readOnlyHint=true and openWorldHint=false already covering the safety profile, the description still adds meaningful behavior: it discloses the failure mode ('Returns an error when the code does not exist') and describes the language-dependent response content. That is substantive context beyond what the 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 purpose and sibling routing are front-loaded, and the long enumeration of return fields is justified because no output schema exists. It is dense but every clause earns its place; only the run-on length keeps it from a 5.

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 read-only lookup with no output schema, the description fully compensates by enumerating the returned fields (status, trilingual labels, sector/group, URL, official legal text) and noting the error case. An agent has everything needed to call it correctly and interpret the result.

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 100%, and each parameter (code pattern, lang enum, country default) is already documented in the schema. The description adds no syntax or format detail beyond the schema's own example, 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?

The description opens with a specific verb+resource ('Get one activity of the Algerian CNRC nomenclature by its six-digit code') and enumerates exactly what the record contains. It distinguishes itself from the sibling search_activity_codes explicitly, so an agent can route between lookup-by-code and search without opening either 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?

It states two concrete when-to-use conditions: 'when the user already gives a code' and 'after search_activity_codes'. This is an explicit routing rule to the alternative tool, leaving no ambiguity about which to call.

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