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

With no annotations, the description carries the full behavioral burden. It usefully discloses that the math is deterministic closed-form with no approximations and states the x402 price ($0.01/call, USDC on eip155:8453), but it never describes the return value (an APY %) or handling of edge cases like rate=0 or negative rates.

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?

Front-loaded with the core conversion, then determinism and pricing. The "Use this when an agent needs to nominal rate → effective yield" sentence largely restates the opening and is slightly garbled, costing a little efficiency but not much.

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 two-parameter, fully-schema-documented pure-math tool with no output schema, the description covers purpose, determinism, and cost. It leaves the output form (APY %) and the title's implied bidirectional '↔' conversion unexplained, which is a minor gap.

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%, so the schema already documents ratePct (APR %) and the compounding enum. The description's mention of "any compounding frequency including continuous" marginally reinforces the enum but adds no syntax or format detail beyond the schema, so baseline 3 applies.

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 (Convert) and resource (APR to APY) with scope (any compounding frequency including continuous), and it clearly distinguishes itself from generic siblings like calculators_compound_interest_calculator by framing the DeFi yield-decisions use case.

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?

"Use this when an agent needs to nominal rate → effective yield, any compounding" gives clear triggering context. However it names no alternatives or exclusions, so the agent is not told why to pick this over compound_interest_calculator or crypto_yield_pools.

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