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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the description's restatement of 'read-only, no network, no stored state, deterministic' adds little. What it does add that structured fields lack is concrete operational limits: 64 KB JSON input, 1 s per call, 1 MB result — the kind of constraint an agent needs to avoid oversized calls.

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?

Front-loaded with the core operation, then when/not-for/side effects/limits in tight order. The main cost is that the English block is a near-verbatim duplicate of the Spanish block, effectively doubling length, though each individual sentence still carries 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?

An output schema exists, so return-value explanation is unnecessary; the description instead covers what schemas cannot — side-effect profile, determinism, and hard limits on input size, latency, and result size. Nothing an agent needs to call this 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?

Schema coverage is 100% and the single parameter is fully documented, so baseline would be 3. The description adds transformation semantics ('rows become columns') and the 20×20 bound, which explains what the array-of-rows structure will produce rather than merely restating its shape.

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 verb+resource (matrix transpose, rows to columns) with a concrete size boundary (up to 20×20), and explicitly names the sibling it is not (matrix-multiply). An agent can distinguish it from matrix-determinant, matrix-inverse, and matrix-multiply without opening any 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?

'Not for: multiplying two matrices (matrix-multiply)' is an explicit exclusion that routes to the correct sibling. The positive 'When: a numeric result has to be exact or reproducible instead of estimated' is clear but generic — it would equally describe matrix-determinant or matrix-inverse, so it does not fully disambiguate among the matrix family.

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