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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so safety is covered structurally. The description adds genuinely new context: 'Read-only, no account' (no auth needed) and 'Returns one JSON object of counters' (return shape), which the annotations do not convey.

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 sentences, front-loaded with the core purpose before usage guidance and the read-only note. The middle enumeration of counters is dense but each item is distinct and informative, so it earns its place, though it could be tightened.

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 input parameters and no output schema, the description carries the full burden and discharges it: it enumerates the returned counters and states the return container type. An agent has everything needed to decide to call it and interpret the result.

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 tool takes zero parameters, so the schema has nothing to document and the baseline is 4. The description's field enumeration describes output, not inputs, which is appropriate and adds no misleading parameter information.

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?

Specific verb and resource ('Returns the registry in numbers') followed by an enumeration of the exact counters returned (agents by protocol, declared tools, checked counts, x402 endpoints, Base settlements, traffic). It explicitly distinguishes itself from the per-agent siblings with 'it says nothing about any one agent'.

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 usage context ('Use it to size the registry or cite figures') and an implicit exclusion ('says nothing about any one agent'), which routes an agent to get_agent for single-entity questions. It stops short of naming the alternative sibling explicitly, so not a full 5.

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