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

With no annotations, the description carries the full behavioral burden. It fully discloses the behavior: pure arithmetic addition with a returned sum. There are no side effects, external dependencies, or hidden behaviors for such a simple operation.

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, clear, front-loaded sentence. Every word earns its place, and there is no redundant or tangential information.

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 simple numeric inputs, a precise operation, and a predictable output, the description plus input schema is complete. No output schema is needed because 'returns the sum' fully specifies the result.

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 provides only names and types for a and b, with no descriptions. The tool description says 'two numbers,' which loosely maps to a and b, but it does not add meaningful semantic context beyond what the schema already declares. For such simple numeric parameters, this is adequate, but the description does not significantly compensate for the 0% schema description coverage.

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 and resource: 'Adds two numbers and returns the sum.' This clearly defines the tool's operation and output. There is no ambiguity between this and siblings like echo or 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 this tool: whenever an arithmetic sum of two numbers is needed. It does not explicitly discuss exclusions, but the sibling tools are unrelated, so no direct alternative-routing guidance is necessary.

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