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

Annotations declare readOnlyHint and openWorldHint, and the description goes further by disclosing the upstream source (mempool.space), a per-successful-call price with the x402 payment rails, and the fact that failed calls are not charged. It also notes unconfirmed-transaction and replace-by-fee handling. Only rate limits or error semantics are absent.

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-loads the resource and lookup key, then packs return fields, source, disclaimer and pricing into a compact block with no filler sentences. Every clause carries either selection signal or behavioral context.

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 the return-field enumeration is not strictly required, but combined with the disclosed source, cost model and payment failure policy the description gives an agent nearly everything needed to call it. Only guidance on failure/retry behavior is missing.

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 ('Transaction id, 64 hex characters'), which sets the baseline at 3. The description restates the lookup key as 'txid' but adds no format, normalization, or edge-case guidance beyond the schema.

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 ('A Bitcoin transaction by txid') and then enumerates the exact returned fields, so an agent can distinguish it from btc_address, btc_fees, evm_tx and solana_tx without opening any schema. The chain and lookup key are both explicit.

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?

Usage is implied by the txid lookup and the mempool.space source, but there is no explicit when-to-use statement and no mention of alternatives (e.g. evm_tx for EVM chains or btc_address for address-level data). The agent must infer routing from the name alone.

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