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

Goes well past the annotations by disclosing the pricing model ($0.01/call, first 25 free, failed calls free), the 404-on-unknown-hash behavior being uncharged, and that repeated identical calls are charged again — which explains and reinforces the idempotentHint=false annotation rather than contradicting it.

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, returned fields, sibling routing, parameter format, error behavior and cost all appear in a compact block with the core purpose front-loaded. It runs long as a single paragraph and the pricing sentence is dense, but no sentence is truly wasted.

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, yet the description names the returned fields, the error case (404, uncharged), the input format, and the billing implications — everything an agent needs to decide to call it and to interpret a failure.

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%, so the schema already documents the single hash parameter. The description still adds value by restating the 0x-prefixed 64-hex format and supplying a concrete example hash, which makes correct invocation easier without contradicting 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+resource ('Look up an Avalanche transaction by hash') and enumerates the fields returned (sender, recipient, value in AVAX, nonce, gas limit, selector, block). It explicitly distinguishes itself from the two nearest siblings, avax_receipt and avax_logs.

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 the selection rule directly: use this to see what was sent or whether it exists, use avax_receipt for success/failure and fees, use avax_logs for emitted events. Both alternatives are named with the condition that selects them, leaving nothing to inference.

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