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

No annotations are supplied, so the description carries the full behavioral burden, yet it only restates the operation. It does not specify input format, expected output (e.g., list of diagonal elements), whether the matrix must be square, or error behavior.

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 front-loaded and extremely brief, which is appropriate for the operation. However, it borders on under-specification rather than true conciseness for a tool with two ambiguous parameters.

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 matrix operation tool with no annotations, no output schema, and ambiguous parameter semantics, the description should clarify input format, output shape, and edge cases. None of this is present.

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 ('m', 'matrix') are documented in the schema, so baseline 3 applies. The description doesn't clarify the ambiguous relationship between 'm' and 'matrix' or their formats, so it adds no value beyond the schema.

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 operation and resource (matrix diagonal), so it's clear in isolation. But it's a tautological restatement of the name/title with no differentiation from numerous matrix siblings (x402-matrix-trace, x402-matrix-flatten, x402-adjacency-matrix, etc.). An agent cannot tell whether this returns a diagonal vector, a sum, or validates a diagonal matrix.

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?

No when-to-use, when-not-to-use, or alternative guidance is provided. With hundreds of matrix/number siblings, the absence of any routing information is a serious gap.

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