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

Annotations already mark this as read-only, idempotent, and non-destructive, so the bar for extra behavioral disclosure is lower. The description still adds value by specifying the exact return fields, that results come as a list, and showing a concrete invocation example. No contradiction 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?

The description is compact and front-loaded, with each sentence earning its place: what the tool returns, how to filter, and an example invocation. No filler or redundant restatement of the name or annotations.

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 simple read-only lookup tool with no output schema, the description is complete: it explains the return format, the optional filtering behavior, and the API key handling is covered in the schema. An agent has enough context to select and invoke this tool 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?

Input schema coverage is 100%, so the schema carries most parameter meaning. The description adds beyond this by clarifying that country and type are optional filters, tying them to the result fields, and providing a usage example. This is a modest but real improvement over the schema alone.

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 resource ('API Ninjas inflation'), the data returned (monthly/yearly rates by country), and the optional filters. It clearly distinguishes this from sibling tools by tying it to inflation rates and outlining the result structure.

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 makes the tool's context clear: use it to retrieve latest inflation rates by country, optionally filtered by index type. It does not explicitly name alternatives or exclusion criteria, but none of the sibling tools are inflation-specific, so the intended usage is easy to infer.

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