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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and closed-world behavior, so safety is fully covered. The description adds that results include caveats and the tools that read each domain, but with an output schema present it does not need to enumerate return shape; no auth, rate, or freshness behavior is disclosed.

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 the resource and its contents and closing with the call-to-action. Every clause adds distinct information and nothing is repeated from the title or annotations.

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?

For a zero-parameter discovery tool with full annotation coverage and an output schema, the description supplies the two things structured fields cannot: what the catalog contains and when to invoke it first. It is nearly complete; only a hint about what to do after reading the catalog (which sibling to call next) is missing.

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 and the schema cannot be enriched. Baseline for a no-parameter tool is 4.

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 names a specific resource — the catalog of public GTM data domains — and enumerates what it covers (filters, id/URL patterns, timestamps, caveats, reading tools), which separates it from sibling retrieval/search tools. It is a noun phrase rather than a verb-led statement of action, so the 'what it does' is implied as a listing/discovery call rather than stated outright.

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?

'Start here when unsure what to ask for' gives an explicit entry-point condition that no sibling offers. It does not name when to skip it or which sibling to go to once the domain is known, but the positive routing guidance is clear.

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