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

Annotations already establish readOnly, idempotent, closed-world, non-destructive behavior, so the bar is lower; the description still adds meaningful context by disclosing that output is static per version, includes a changelog, and documents shared conventions like tier, delay, timestamps and missing-data reporting. It does not say what format the guide is returned in or how large it is, which is the only notable omission.

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 sentences, front-loaded with what the tool is before listing contents; every clause adds a distinct piece of information. The trailing 'No inputs; static per version' is slightly clipped in style but earns its place by ruling out request parameters and caching concerns.

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 of explaining what comes back, and it does so by enumerating field attributes, response conventions, and the changelog. An agent knows what it will get, though the concrete structure/format of the returned guide is left unspecified.

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?

Zero parameters, so the baseline is 4; the description explicitly confirms 'No inputs' and explains why (static per version), which reinforces the empty schema rather than leaving it to inference. No further parameter detail is possible or needed.

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 ('static, versioned dictionary of every field this surface emits') and enumerates its contents: unit, value set, one-sentence meaning, shared response conventions, and a changelog. This cleanly separates it from all siblings, which are data-retrieval or mutation tools, not schema references.

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 framing as a dictionary of 'every field this surface emits' plus 'how missing data is reported' makes its role as an interpretation aid for other tools' responses clear. It stops short of explicitly saying when to call it (e.g. 'consult before interpreting tier/delay/timestamp values') or naming a competing source of field semantics.

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