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

With no annotations, the description must carry the behavioral burden. It usefully discloses that rows are not shape-checked and that a short row produces NaN entries, which is real edge-case value. However it says nothing about required permissions, return format, or whether both aliases must be supplied, leaving significant gaps for a mutation-free but unannotated tool.

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 functional sentence is front-loaded and tight, but the trailing "🆓 5 free trial calls per signed wallet" is promotional noise that does not help an agent invoke the tool correctly.

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 annotations, no output schema, and 0% parameter coverage, the description should cover input format, required-vs-optional aliases, and return shape. It covers only purpose and one edge case, leaving the agent unable to construct a correct call with confidence.

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 0% and there are 4 parameters, so the description should compensate. It hints that a/m1 and b/m2 are alternative spellings of the two operands, which is genuinely useful, but it never explains how a matrix is encoded in a string (row/column delimiters) or whether one of each alias pair is required.

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 names a specific verb and resource ("Computes the element-wise sum of matrices") that cleanly distinguishes it from sibling math tools like x402-matrix-sub and x402-matrix-multiply. It does not explicitly contrast itself with those siblings, but the operation is unambiguous.

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?

There is no statement of when to prefer this tool over x402-matrix-sub/multiply or when it is inappropriate. The only usage-adjacent content is a caveat about shape handling, not guidance on tool selection or prerequisites.

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