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

Even though readOnlyHint is already present, the description adds substantial behavioral detail: the exact components of the index, a clarification that the index concerns rates not income, and a documented fallback to the country index when fewer than four services have bike rates. This goes well beyond the annotation.

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 three sentences and each adds value: core output, semantic clarification, and fallback behavior. It is appropriately front-loaded and not padded, though it could be tightened slightly.

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?

The description covers return contents and an important fallback edge case, which is helpful given no output schema. However, it leaves the transport parameter ambiguous and provides no selection guidance, so the description is not fully complete for the tool's complexity.

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 0%, so the description must explain the parameters, but it only implicitly references city and delivery method. It does not explain the optional transport enum, how filtering behaves, or the meaning of each transport value. This is a clear gap for correct invocation.

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 clearly states that the tool returns rates for all services in a city by delivery method, plus a courier rate index. The resource and content are specific, and the tool name aligns. However, it does not explicitly contrast with sibling tools like get_service or calculate_income, so differentiation is implied rather than explicit.

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 implies this is the tool for city-level delivery rates and an index, and explicitly clarifies it is not about income. However, it does not name a sibling alternative or state conditions for when to choose this tool over others.

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