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

With no annotations, the description carries the full burden and does disclose non-obvious traits: the cost model ('$0.005 per call') and the payment rail ('x402 (USDC)'), plus the underlying RPC method. It omits what happens if 'chain' is omitted (default chain?) and any error behavior for unsupported chains, so it is strong but not complete.

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?

Three short sentences, each earning its place: return values first, then the decision it supports, then implementation and pricing. Front-loaded and free of filler.

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?

With no output schema and no annotations, the description must carry everything, and it does explain the returned fields and cost. The remaining gap is behavior when 'chain' is absent and error handling for invalid chains, which an agent would still need to discover.

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% and the sole parameter's allowed values (base | ethereum | polygon | arbitrum | optimism) are already in the schema. The description adds only the phrase 'any supported chain', which hints at the domain but not at default behavior when the optional parameter is omitted. Baseline 3 applies.

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 resource and the exact values returned ('latest block height and timestamp', 'how old the chain head is in seconds'), and grounds it with the underlying RPC method (eth_getBlockByNumber). An agent can distinguish this from siblings like evm_chains (lists chains), evm_tx, or evm_fees without opening 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 a clear usage context: 'Tells an agent whether a node is in sync,' which is exactly the decision this tool supports. However, it names no alternatives (e.g., evm_chains for enumerating supported chains) and states no when-not-to-use condition, so it stops short of explicit routing guidance.

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