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

Annotations already cover the safety profile (readOnlyHint, destructiveHint=false, openWorldHint), but the description adds substantive context beyond them: 404 returns are uncharged, pricing is $0.01/call via x402 USDC or a card key, the first 25 calls are free, failed calls are free, and repeats are not free. That last point meaningfully explains the idempotentHint=false annotation. It stops short of describing response shape details like pagination or formatting, but for a single-lookup tool that is a small gap.

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 return fields, then sibling routing, then input format, then pricing — a sensible priority order with no filler. Slightly overpacked: the charging point is stated twice ('Price $0.01/call... failed calls free' and 'each call is charged, so repeats are not free'), which could be one clause.

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, so the description compensates by listing the returned fields, and it also covers input format, error semantics, and cost. For a one-parameter read lookup, an agent has everything needed to call it correctly and interpret 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?

Schema coverage is 100% and the single parameter is fully documented in the schema, so the baseline would be 3. The description earns an extra point by adding a concrete worked example hash and pairing the format constraint with the 404-on-unknown-hash consequence, which tells the agent what a well-formed value looks like in practice.

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 ('Look up a Sei transaction by hash') and enumerates the exact fields returned (sender, recipient, value in SEI, nonce, gas limit, function selector, block). This makes it immediately distinguishable from sei_receipt and sei_logs, which are named as different scopes.

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?

Explicitly names both when to use it ('to see what was sent or whether it exists') and which siblings cover the excluded cases ('for success or failure and fees paid use sei_receipt, for emitted events sei_logs'). Also states the 404 path for unknown hashes, so the agent knows the failure mode is expected rather than an error to retry.

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