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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is fully covered by structured data. The description only adds the same-size precondition; it says nothing about error behavior when dimensions mismatch or about output shape, though the output schema covers return values.

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 front-loaded sentence with no filler; the key constraint ('same-sized') is placed where it will be read first. Nothing could be removed without losing meaning.

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 an output schema present, annotations covering safety, and full parameter documentation, the description covers what an agent needs to invoke the tool correctly. The only gap is unstated behavior on dimension mismatch, which is minor for a simple pure-function calculator.

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%, with both parameters documented as 'First matrix' and 'Second matrix' plus concrete 2x2 examples. The description adds only the semantic constraint that both must share dimensions, which is marginal beyond what the schema already conveys.

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?

States a specific operation (element-wise addition) on a specific resource (two same-sized matrices), which is far more precise than the title alone. It does not explicitly distinguish itself from close siblings like calculator_matrix, calculator_matrix_multiply, or calculator_matrix_inverse, so an agent must infer the distinction from the operation semantics.

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 phrase 'same-sized matrices' implies the precondition for correct use, which is useful implied guidance. However, there is no explicit when-to-use statement, no mention of when not to use it, and no routing to the multiply/inverse/matrix siblings.

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