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

Annotations only declare readOnlyHint/openWorldHint; the description adds substantial context beyond them: no broadcast occurs, the paid x402 cost, chain-specific simulation backends (eth_simulateV1 vs simulateTransaction), chain support (7 networks), and the shape of the result including revert reason and risk level.

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 purpose and effect ('what leaves and enters the wallet'), then mechanics, then cost. The single dense enumeration is entirely informational — no filler, no restatement of the title 'simulate tx'.

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 7-parameter, no-output-schema tool, the description supplies everything an agent needs: supported chains, the EVM-vs-Solana invocation split, that broadcast does not happen, cost, and the returned fields including failure signalling via revert reason.

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 baseline is 3, but the description adds real semantics the schema lacks: which parameters belong to the EVM raw-call path (from, to, data, value) versus the Solana path (base64 transaction), and that Solana payloads may be unsigned.

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 ('Simulate a transaction before signing it') and enumerates the exact outputs an agent gets (balance deltas, approvals, revert reason, gas/fee, risk level). This clearly separates it from siblings such as explain_transaction (post-hoc analysis), swap_route (routing) and token_flows without needing to open any schema.

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 clear triggering context: pre-signing, with an explicit 'Nothing is broadcast' exclusion and the paid/price model ($0.0015, x402). It does not name a sibling to use instead when the transaction is already on-chain (e.g. explain_transaction), so it stops short of full when/when-not routing.

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