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

No annotations are provided, so the description carries the full burden. It does disclose a genuinely useful non-obvious trait – the pay-per-call model with '5 free trial calls per signed wallet' – which is real behavioral context. However, it says nothing about failure modes such as invalid or degenerate triangles, which matters for a geometry computation.

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 compact sentence with the value proposition front-loaded, followed by a short pricing note. Nothing is padded, though the emoji and trial-pricing clause are only marginally relevant to invocation.

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 zero parameter documentation, the description is the only source of truth – and it leaves the three inputs undefined while mischaracterizing them. An agent cannot reliably call this tool without guessing what a, b, and c mean.

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% for three parameters named only 'a', 'b', and 'c', so the description must compensate and it does not. Worse, the phrase 'from its area and semiperimeter' points at inputs that do not exist in the schema, actively misleading the agent about what a, b, c represent.

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 ('Returns a triangle's inradius'), which is reasonably clear, but it contradicts itself on inputs by saying the value comes 'from its area and semiperimeter' while the schema accepts sides a, b, c. It also makes no attempt to distinguish itself from close siblings such as x402-triangle-circumradius, x402-triangle-area, or x402-triangle-heron.

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 when-to-use guidance and no mention of alternatives, despite a dense cluster of near-identical triangle tools in the sibling list. An agent has no stated basis for choosing this over x402-triangle-circumradius or x402-triangle-heron.

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