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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered; the description adds non-obvious behavior beyond them: per-call price ($0.003), a free tier (10/day), an x402 payment-required result after the quota, and that errors return isError and are not charged. That is precisely the context annotations cannot express.

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 capability, then labeled 'When to use', 'Price', and 'Errors' segments — every sentence carries information. It is slightly dense with commercial detail, and the parenthetical 'callable here by name' is mildly noisy, but there is no true filler.

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?

An output schema exists, so return structure needn't be re-explained; the description still sketches the payload at a useful level (status, fee, named programs, balance deltas, summary). Combined with pricing, quota, and error semantics, an agent has everything needed to call it correctly and anticipate the outcome.

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?

There is a single parameter with 100% schema description coverage (base58, 64-90 chars, regex pattern). The description adds no format or syntax detail beyond the schema, so the baseline of 3 applies — the schema does all the work here.

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+resource ('turns any Solana transaction signature into plain facts') and enumerates exactly what is produced: status, fee, named programs, per-owner SOL/token balance changes, summary. It also explicitly names the non-Solana case (0x hashes → evm_tx), so an agent can separate it from other sibling lookup tools without opening the 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?

Provides an explicit routing rule: 'For Solana signatures; for 0x hashes use evm_tx'. It also covers the failure path (works for failed transactions, includes error log lines), leaving no ambiguity about when this tool applies versus an EVM equivalent.

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