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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds valuable behavior beyond annotations: it performs two internal calls, costs $0.001 USDC, and explains the real-world consequence of a mismatch. This enriches the behavioral model without contradicting annotations.

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?

The description is compact – three sentences that front-load the core purpose, then add cost and chain list. No filler or redundant phrases. It could be slightly tighter (e.g., merging chain list with schema) but is well-structured and easy to scan.

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 one-parameter tool with an output schema, the description covers the essential context: what it does, cost, supported chains, and an endpoint reference. It doesn't explain the output structure, but that's already provided by the output schema. No critical missing detail for an agent 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 description coverage is 100% – the single parameter 'chain' is fully described with an explicit list of accepted values. The description repeats that list and adds the example endpoint URL, but does not introduce new syntactic meaning. Since the schema already carries full parameter semantics, a baseline of 3 is appropriate; slight credit for the endpoint mapping, but not enough for a 4.

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?

The description clearly states the tool's function: comparing eth_chainId and net_version for a given chain. It explains the purpose (safety check against signing on the wrong network) and distinguishes it from other chain_* tools by focusing on ID agreement rather than balances, blocks, or calls. The verb 'check' and resource 'chain ID vs network ID' are specific and unambiguous.

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?

The description gives strong context for when to use it ('two-call safety check'), notes the cost, and lists supported chains. It doesn't explicitly name alternatives or say when not to use it, but there are no direct siblings (e.g., no other tool checks chain ID agreement), so the guidance is adequate. The endpoint equivalence adds helpful practical context.

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