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

With no annotations provided, the description carries the full behavioral burden. It discloses that the operation is a pure computation that returns the sum, implying no side effects. It does not mention edge cases like floating-point precision, but that is acceptable for a simple adder.

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 a single concise sentence with no wasted words, front-loading the core purpose and result.

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, stateless arithmetic operation, the definition is complete. The input schema defines both required parameters, and the description explains the output behavior ('returns the sum'). No output schema exists, so the explicit return description is necessary and sufficient.

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 schema has 0% description coverage, so the description must compensate. It states 'two numbers', implicitly clarifying that a and b are the addends, which adds meaning beyond the raw schema. It does not elaborate on individual parameters, but the parameter names are self-explanatory.

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 a specific verb 'adds', names the resource 'two numbers', and states the outcome 'returns the sum'. It clearly distinguishes this tool from unrelated siblings echo and server_time.

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 clearly implies when to use the tool: anytime two numbers need to be summed. It does not explicitly compare with alternatives, but the siblings are unrelated (echo, server_time), so no confusion exists.

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