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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so the safety profile is covered. The description adds one genuinely useful trait beyond that: the result is counts only and contains no per-identity data. It says nothing about refresh cadence, aggregation window, or response shape, so the added value is modest.

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?

Two short sentences with no filler, and the privacy/scoping note is front-loaded rather than buried. It is arguably over-compressed, trading clarity for brevity, which keeps it short of a 5.

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 parameters and no output schema, the description carries the burden of explaining what comes back. It hints at counts but never specifies what is counted (records? keys? time window?) or the response form, which leaves a real gap for a zero-arg tool whose only value is its return data.

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 there is nothing for the description to disambiguate; baseline 4 applies. Schema coverage is reported at 100% with an empty property set.

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 conveys that this returns recorded volume plus a count of distinct external keys, which reads as usage/statistics retrieval, but the phrasing ('How much is recorded, and by how many keys that are not ours') is oblique and never states a clear verb+resource. It also gives no differentiation from siblings like get_chain or get_ledger_attestation, leaving the agent to infer this is the aggregate-stats tool.

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?

There is no explicit when-to-use guidance, no prerequisites, and no mention of alternatives among the seven sibling tools. The agent gets a vague sense of what the tool returns but nothing about when to reach for it versus the proof/ledger tools.

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