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

Annotations already mark this read-only, idempotent, and non-destructive. The description adds valuable behavioral context: it costs $0.001 USDC, supports seven chains, is byte-identical to a REST endpoint, and returns syncing status plus head information. This meaningfully extends beyond the structured 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 and front-loads the most important insight — why sync status matters. Each sentence earns its place: purpose, cost, supported chains, and REST equivalence. The phrasing 'eth_syncing plus the head' is slightly jargon-heavy, but it is not wasteful.

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 a single well-documented parameter, an output schema, and strong annotations, the description provides enough additional context: the reason to call the tool, pricing, chain support, and an equivalent REST call. It is sufficiently complete for an agent to select and 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?

The input schema already documents the chain parameter with all supported values and marks it required, so schema coverage is 100%. The description restates the supported chains and includes an example REST-style path, but adds little new parameter-level meaning beyond that baseline.

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 communicates what the tool reports — sync status plus the head block — and frames it as a way to detect a node that is behind. The title reinforces this. It does not explicitly name a sibling alternative, but its function is clearly distinct from the many chain_* data tools.

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 opening sentence gives a concrete usage context: use this when stale node data might contaminate other responses, since nothing else in a typical response reveals this. It stops short of explicitly naming when not to use it or pointing to an alternative, but the guidance is clear and practical.

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