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

Beyond the sparse annotations (readOnlyHint false, idempotent false), the description discloses that source records are not modified, details the x402 cost, states that a successful paid call consumes the advertised payment, notes that the payment-required challenge is free, and warns that repeated calls may require a new payment. It also mentions accepted networks and the limitation that history is not a complete legal or commercial event timeline. This is rich, valuable behavioral context.

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 well-structured with clear sections (use/avoid, limitations, price, paid-call behavior, accepted networks) and each sentence contributes operational value. It is longer than a minimal description, but the payment and network details are warranted for correct invocation, so no material clutter.

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 single-parameter tool with a high-coverage schema and an output schema, the description is nearly complete. It provides selection guidance, pricing, payment behavior, network restrictions, and limitations. The only minor gap is a lack of explicit mention of the required 'identifier' parameter in the description text, but the input schema and title cover this.

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%: the schema already explains the identifier parameter as '9-digit SIREN or 14-digit SIRET' and that a SIRET is normalized to its SIREN. The tool description does not add any further parameter-level meaning beyond that already present, 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 states a specific verb and resource: 'Returns the historized Sirene periods of a French legal unit,' and enumerates the included fields (status, name, legal form, activity, headquarters NIC, change flags). It also differentiates from the sibling tool company/fr/events by explicitly naming it, making selection behavior unambiguous.

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 gives explicit usage guidance: 'Use when you need the exact Sirene period history for a French legal unit' and 'Avoid when you need a BODACC event timeline; use company/fr/events.' This provides both a clear condition and a sibling alternative, leaving no ambiguity about when to choose this tool.

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