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

No annotations are provided, so the description carries the full behavioral burden. It discloses the payment model (free trial calls per signed wallet) but says nothing about validation behavior for non-triangle inputs (a+b>c), error modes, or output format/units, which matters for a computation tool with no output schema.

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 compact clauses with the core operation front-loaded and the pricing note appended. Nothing is padded, though the emoji/pricing tail is marketing rather than specification.

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 3-parameter computational tool with no annotations, no output schema, and 0% schema description coverage, the definition should at minimum state input units, required-ness (all three sides are mathematically required but the schema marks none as required), and invalid-triangle handling. None of that 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 coverage is 0% and the three parameters are named a, b, c with no types beyond 'string' and no descriptions. The phrase 'from three sides' faintly implies these are side lengths, but the description never maps a/b/c to the sides, states units, or explains the string encoding of numeric input.

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 and resource: 'Returns a triangle's area from three sides with Heron's formula.' An agent can tell this is a geometry-area computation. It does not, however, differentiate itself from the sibling x402-triangle-area, which appears to do the same thing, so it falls short of a 5.

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 guidance and no mention of the near-identical sibling x402-triangle-area or any exclusions. The only contextual sentence is about billing ('5 free trial calls per signed wallet'), which is a pricing note, not usage guidance.

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