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

Annotations already declare read-only, idempotent, non-destructive, closed-world behavior. The description goes further by disclosing input formats and the return shape (exact sum matrix plus a per-position calculation), which the annotations do not cover.

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?

Two sentences, no filler. The core operation and dimension constraint are front-loaded, followed by accepted formats and the return shape.

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?

With no output schema, the description commendably states what is returned. It covers the input constraint and formats; only the failure mode for mismatched dimensions is left unstated.

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 coverage is 100% and both params have descriptions, so the baseline is 3. The description adds real meaning beyond the schema: accepted value formats (integers, decimals, fraction strings like 1/2) and the equal-dimensions requirement, which the schema does not enforce.

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?

Specific verb+resource ('Add two matrices') with the key constraint ('of the same dimensions entry by entry'). 'Add' naturally contrasts with the subtract/multiply siblings, so an agent can distinguish it without opening the schema.

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?

'Useful for exact matrix addition or explaining each entry step by step' gestures at when to use it, but is largely restating the purpose rather than naming conditions or alternatives among matrix_subtract/matrix_multiply. Usage is implied, not spelled out.

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