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

Annotations already declare the tool safe (readOnlyHint=true, idempotentHint=true, destructiveHint=false). The description adds valuable behavioral context: it explains the meaning of the 'year' field differs by family, notes the inclusion of conversionDate and installments for Renda+/Educa+, and clarifies that simulate_bond may synthesize bonds outside the catalog. This goes beyond annotations by explaining output semantics and edge cases.

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 a bolded primary directive, bullet points for family-specific details, and a clear returns statement. It front-loads the most important information (usage before simulate_bond) and then provides necessary nuances efficiently. No redundant sentences; every part adds value.

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 catalog listing tool, this description is complete. It covers the return schema, explains ambiguous fields (year, conversionDate), notes the historical simulation caveat, and directly addresses the main use case. An agent can confidently call this tool and interpret results without additional documentation.

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?

The tool has zero parameters, so schema coverage is trivially 100%. The description does not need to explain any parameters but instead documents the output structure in detail, which is the real semantic content. A baseline of 4 is appropriate given the absence of parameters and the clear return format.

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 and resource: 'Lists every Tesouro Direto bond currently in the official catalog, grouped by family.' It also explicitly ties its purpose to the sibling simulate_bond by saying 'USE THIS BEFORE calling simulate_bond to discover available bonds, or to disambiguate a user's reference.' This clearly differentiates it from other tools that focus on prices or simulation.

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?

Provides explicit usage context: use before simulate_bond to discover bonds or to disambiguate maturity dates. It also warns that simulate_bond accepts bonds outside this catalog, helping the agent decide when this tool is insufficient. This is unambiguous and covers both when to use and when not to rely solely on it.

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