ga4_get_custom_definitions

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

With no annotations, the description carries the full burden of disclosing behavior. It explicitly labels the operation 'Read-only' and says it lists metadata-exposed definitions, but it does not describe output shape, pagination, error behavior, or what 'fallback' means in practice.

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?

A single sentence front-loads the core action and resource, then adds the read-only fallback context. There is no filler or duplication of schema content.

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 one-parameter read-only list tool, the description adequately states the input and what will be returned (custom dimensions and metrics). The main residual gap is explaining the 'fallback' behavior and any limitations of the metadata source.

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?

Schema coverage is 100% and the only parameter, propertyId, already has a clear schema description including a numeric example. The description adds no additional parameter-level meaning, so the baseline of 3 applies.

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 verb ('List') and a distinct resource ('custom dimensions and custom metrics'), so an agent can distinguish it from generic metadata tooling such as ga4_get_metadata. The phrase 'Read-only fallback for custom definition inventory' is slightly ambiguous, which keeps this from a 5.

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 'Read-only fallback for custom definition inventory' phrase implies a fallback use case, but it does not explicitly state when to use this tool instead of ga4_get_metadata or an admin custom-definition endpoint. No exclusion or alternative is named.

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