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 does disclose a pricing/auth trait ('5 free trial calls per signed wallet'), which is useful, but says nothing about whether the result includes taxes/insurance, rounding, currency, 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?

One sentence, front-loaded with the verb and resource, no padding. The emoji promo line is minor promotional noise but does not obscure the core statement.

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 6 undocumented string parameters, zero required markers, no annotations, and no output schema, the description leaves the agent guessing about which inputs to supply and in what format. A calculation tool with this much schema ambiguity needs explicit parameter reconciliation.

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% across 6 parameters, so the description must compensate. It names three concepts (principal, annual rate, term in years) but never explains the apparent aliases (apr vs rate, term vs years, amount vs principal), which are strings with no type or format guidance, nor which are 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?

States a specific verb and resource: 'Computes the monthly payment for a fixed-rate mortgage.' That is clear and agent-legible, but it does not differentiate itself from near-duplicate siblings such as x402-mortgage-payment or x402-loan-payment, so an agent cannot tell which one to pick without inspecting schemas.

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, no exclusions, and no mention of alternatives. With a sibling named x402-mortgage-payment sitting right next to it, the absence of routing guidance is a real gap.

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