Example MCP Server

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

No annotations are provided, so the description carries the full burden of behavioral disclosure. 'Multiply two numbers' indicates a computational operation but doesn't describe traits like error handling (e.g., overflow), performance, or output format. For a tool with zero annotation coverage, this is a significant gap in 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 extremely concise with 'Multiply two numbers'—a single, front-loaded sentence that wastes no words. Every part earns its place by directly stating the tool's function, making it efficient and easy to parse for an agent.

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?

Given the tool's simplicity (two integer parameters, no annotations, no output schema), the description is incomplete. It lacks information on output (e.g., returns the product as an integer), error cases, or usage context relative to siblings. For a basic computational tool, more detail would help the agent understand the full scope.

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 schema provides no parameter descriptions. The description 'Multiply two numbers' implies two parameters (the numbers to multiply) but doesn't add meaning beyond what the schema's property names ('a' and 'b') suggest. It compensates minimally by indicating the operation, but doesn't detail parameter types or constraints, aligning with the baseline when schema coverage is low.

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 'Multiply two numbers' clearly states the verb (multiply) and resource (numbers), making the purpose immediately understandable. It distinguishes from siblings like 'add' or 'divide' by specifying the mathematical operation, though it doesn't explicitly contrast with them. The description is specific but lacks explicit sibling differentiation, which would require a 5.

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 provides no guidance on when to use this tool versus alternatives like 'add', 'divide', or 'subtract'. It implies usage for multiplication scenarios but offers no explicit context, exclusions, or prerequisites. This leaves the agent to infer usage based on the tool name alone, which is minimal guidance.

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