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

Annotations already declare readOnly/openWorld/non-destructive, and the description layers on genuinely non-redundant behavior: a per-call price ($0.002 USDC), the x402 payment rail and accepted chains (Base, Solana, Polygon, Arbitrum), automatic payment by @x402/mcp clients, and a free sample invocation. This is exactly the auth/cost context an agent needs and cannot get from the 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?

Purpose and return fields are front-loaded, then usage, then payment mechanics. The long enumeration of returned fields is dense but earns its place given there is no output schema; the structure is logical and free of filler, though the field list is slightly run-on.

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?

With no output schema, the description must carry the return contract, and it does so explicitly (status/error, time, checkpoint, sender, calls, gas, balance changes, object deltas, events). Combining that with the payment and usage context, an agent has everything needed to call and interpret this tool.

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 'digest' parameter is fully documented as base58, so the schema carries the burden. The worked example input reinforces the format but does not add semantic meaning beyond what the schema already states, so the 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 and resource ('Look up an IOTA mainnet transaction by digest') and immediately enumerates the returned fields (status, checkpoint, sender, Move calls, gas fee, balance changes, objects, events). This cleanly distinguishes it from sibling read tools like evm_tx, btc_tx, and sui_tx, which target different chains.

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 clear context ('Use to confirm a payment or contract call on IOTA'), so the agent knows the triggering scenario. However, it names no alternatives and sets no exclusions (e.g. iota_verify for notarization checks or iota_watch for monitoring), leaving the routing decision partly to inference.

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