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

With no annotations available, the description carries the full burden of behavioral disclosure. It fully describes the operation (adding two numbers) and the return value (the sum), leaving no room for hidden side effects, state changes, or other behaviors. For a pure arithmetic function, this is complete transparency.

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, efficient sentence with no redundant words. The core operation and return value are front-loaded, and there is no filler or repetition.

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 tool with two numeric parameters, no annotations, no output schema, and a trivial operation, the description provides all necessary context: what the inputs are, what the tool does, and what the caller receives. Nothing an agent needs to invoke it correctly is missing.

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 input schema only provides names and types (a, b as numbers), with 0% description coverage. The description compensates by clarifying that both parameters are the two addends and that the result is their sum, which gives functional meaning beyond the raw schema. It could only be improved by explicitly naming the parameters.

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 verb ('Adds'), the resource ('two numbers'), and the outcome ('returns the sum'). It is not a tautology of the name and clearly distinguishes this tool from the sibling tools 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 implies the clear context: use this tool when you need to add two numbers and get their sum. While it doesn't explicitly exclude siblings, none of them perform arithmetic, so the context is unambiguous and no exclusions are needed.

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