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

It discloses a pure computation with no side effects, which is consistent with the annotations (readOnlyHint=true, idempotentHint=true, destructiveHint=false). It adds no extra behavioral context beyond those annotations, so the bar is met without being exceeded.

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?

A single, clear, front-loaded sentence with no wasted words. It communicates the operation and result immediately.

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 simple pure-function nature, complete schema with 100% coverage, comprehensive annotations, and an output schema, the description is fully sufficient. No additional context is needed for an agent to call 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?

Schema description coverage is 100% and both parameters already include detailed descriptions and examples. The tool description only repeats 'two numbers,' adding no meaningful semantics beyond the schema, so baseline 3 is appropriate.

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 ('add'), the resource ('two numbers'), and the outcome ('return the sum'). It fully explains what the tool does and is clearly distinct from the unrelated sibling tools.

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 use whenever a sum of two numbers is needed, but it does not explicitly discuss when to use this tool versus alternatives or mention any exclusions. For a trivial arithmetic utility, the implied usage is adequate but not explicit.

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