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

Annotations cover safety (readOnly, idempotent, non-destructive, openWorld), but the description adds the economics and flow the annotations cannot: $0.002 per call, bad input refused before any charge, two payment paths (returned x402 URL vs. automatic paid call with a P0 key and deduction). That is material behavioral context for a paid 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?

Front-loaded with the 'Use when' trigger and the returned fields, which is the right ordering. It is dense but not padded; the long key-purchase URL and parenthetical pricing detail weigh it down slightly, though each sentence still carries actionable information.

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?

There is no output schema, and the description compensates by naming the returned fields and stating that the paid response includes a schema and example. Pricing, charge-safety, authentication options, and the sibling alternative are all present, leaving nothing an agent needs to call it correctly.

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 100% with a regex pattern for hash and a documented enum plus default for chain, so the schema carries the semantics. The description only repeats the chain list and adds no format, constraint, or validation nuances beyond it, 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 resource (transaction receipt) and enumerates exactly what it returns: status, block, confirmations, gas used, effective gas price. It also names the sibling evm_transaction and the boundary between them (receipt outcome vs. transaction fields), so an agent can distinguish them without opening 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?

Opens with an explicit 'Use when you need to know whether a transaction succeeded' trigger and names the alternative 'for the transaction fields (from, to, value, input) use evm_transaction'. Both the when-to-use and the when-to-use-something-else are stated outright.

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