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

Annotations already mark the tool as read-only and idempotent. The description adds meaningful context beyond that: the result is an ESTIMATE based on yield/revaluation/rate assumptions, market assumptions are caller-provided, and interest plus insurance are deductible. No contradiction with the 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?

The description is compact, front-loaded with the scenario and outputs, and includes the essential estimation caveat and methodology source. There is minor redundancy with the annotation title, but the description remains dense and readable.

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 simulation tool with no output schema, the description covers the key outputs, the estimation caveat, and the calculation basis. It does not detail the return structure, but the schema documents all inputs and the tool's purpose is clear enough for correct invocation.

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%, so the input schema already explains every parameter. The description only refers generically to assumptions about yield, revaluation, and rates, adding no specific parameter-level meaning beyond what the schema provides.

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 the verb 'Projette' with a clear resource ('une SCPI financée à crédit') and enumerates the computed outputs: mensualité, effort d'épargne, fonds propres, and TRI. The 'à crédit' qualifier clearly distinguishes this tool from sibling SCPI simulators such as simulateurs_scpi and simulateurs_apport_credit.

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 intended use case is clear: projecting a SCPI purchase financed by a loan, including deductible interest and insurance. It does not explicitly name sibling tools or state when not to use them, so it falls just short of full alternative routing.

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