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

Annotations already cover the read-only/safe profile, but the description adds materially: unknown hash returns 404 and is uncharged, pricing is $0.01/call via x402 USDC or card key with first 25 free, failed calls are free, and repeats are not free (consistent with idempotentHint=false). That cost and error behavior cannot be derived from annotations or 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?

Front-loaded with purpose, then sibling routing, then input format/example, then pricing — a sensible order with no filler sentences. Minor redundancy in restating the hash format already given by the schema, and the pricing clause is dense, but each element carries 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 listing the returned fields; it also covers error behavior (404, uncharged) and the billing model. For a single-param lookup tool, an agent has everything needed to decide to call it and to interpret typical outcomes.

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% and the single hash param is documented there, so the baseline is 3; the description goes further with a concrete example value and the failure semantics of an unknown hash. The format restatement ('0x-prefixed 64-hex') duplicates the schema, so it earns a 4 rather than a 5.

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 ('Look up a Sonic transaction by hash') and enumerates exactly which fields come back (sender, recipient, value in S, nonce, gas limit, selector, block). It also names the two nearest siblings, sonic_receipt and sonic_logs, with the conditions that select them, so an agent can distinguish it without opening any schema.

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?

Gives explicit when-to-use ('see what was sent or whether it exists') and explicit when-not-to-use with the correct alternatives: 'for success or failure and fees paid use sonic_receipt, for emitted events sonic_logs'. This is the routing information an agent needs and nothing is left to inference.

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