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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint, so the safety profile is covered. The description adds meaningful context: data coverage ('all ~30M French legal units registered since 1973') and freshness ('updated daily'), plus the specific fields returned. No contradictions 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?

Three sentences, each with a distinct purpose: identifying the resource and method, enumerating returned data, and providing coverage/update cadence plus sibling routing. No redundancy or 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 one-parameter lookup with an output schema and safe read-only annotations, the description covers what is returned, the data source, update frequency, and alternative tools. An agent has everything needed to call it correctly.

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 already defines the siren parameter as exactly 9 digits, with space-stripping behavior. The description merely repeats '9-digit SIREN identifier' and adds no new semantic value, so the baseline of 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 uses a specific verb ('Retrieve') and names the exact resource: the official record of a French legal unit from the INSEE Sirene registry via a 9-digit SIREN. It lists the returned fields and explicitly contrasts with sibling tools (insee.establishment.by_siret and insee.company.search), making it easily distinguishable.

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 explicitly states when to use alternatives: 'Use insee.establishment.by_siret for physical address and site-level details, or insee.company.search to find companies by name or activity code.' This gives clear routing guidance beyond the generic purpose.

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