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

Annotations already cover readOnly and openWorld, but the description adds crucial behavioral context absent from annotations: pricing ($0.002 USDC per call via x402), automatic payment through supported MCP clients, and a free sample with example input. It doesn't describe rate limits or error cases, but the paid-call mechanics are a significant disclosure beyond structured fields.

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 return values and use cases, then pricing and example. It is efficient but slightly long due to the payment and sample details; still, every sentence carries distinct information needed to call the tool correctly.

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?

For a single-parameter read-only lookup with no output schema, the description covers what the tool does, what it returns in detail, when to use it, payment mechanics, and a sample input. An agent has everything needed to invoke it correctly.

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 schema already defines txid as a 64-hex string. The description only mentions the txid field implicitly through the example, not adding format or validation details beyond the schema. Baseline 3 is appropriate.

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 (lookup a Bitcoin transaction by txid) and enumerates exactly what data is returned (confirmations, block, fee, RBF, inputs/outputs, USD value). Clearly distinguishes itself from sibling tools like btc_address, evm_tx, or token_simulate.

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 two concrete use cases: 'confirm a payment arrived' and 'check why a transaction is stuck.' It doesn't explicitly say when to use btc_watch (which likely monitors) vs this one, but the context is clear enough for an agent.

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