Simulate a read-only call

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

Annotations already declare readOnlyHint=true, so the safety profile is covered. The description adds behavioral insight beyond annotations: 'Nothing is broadcast and no key is used' reinforces the read-only nature and explains the absence of state changes. It also reveals the tool's behavior of reporting whether the call reverted, which is useful. However, it doesn't mention error cases or edge conditions like invalid calldata, but this is minor given 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 two sentences, front-loads the primary action and outcome, and adds the safety note. Every sentence earns its place: the first states the result, the second gives usage context. No fluff.

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?

Given the tool has 7 parameters, no output schema, and moderate schema coverage, the description covers the main use case and outcome. It doesn't list all parameter interactions, but for a simulation tool with readOnlyHint=true, an agent can infer that it is a safe probe. The description could benefit from noting that the call is executed in a simulated environment and may not reflect actual future state, but this is a minor gap.

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 57%, meaning some parameters (to, from, block, value) lack descriptions. The overall description mentions 'calldata and value combinations', which hints at the relevance of data and value parameters. It does not add detail on 'to', 'from', 'block', or 'value' beyond schema, but the description's mention of probing combinations partially compensates. Since coverage is moderate, the description adds moderate value but could provide more per-parameter explanation.

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 performs a read-only eth_call simulation and reports success/revert status, distinguishing it from mutation tools. It specifies the verb 'Simulate', the resource 'call', and the output (returned or reverted). It names the sibling tools that serve similar but distinct purposes (like get_bytecode, read_storage), helping an agent differentiate.

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 explicitly states when to use this tool: 'Useful for probing which calldata and value combinations a contract accepts.' It implicitly warns against using it when actual transaction execution is desired, since it says nothing is broadcast and no key is used. It doesn't explicitly mention alternatives, but the sibling context provides the differentiation. This is strong guidance.

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