GA4 custom definitions

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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description goes beyond them by disclosing quota behavior (50/25/10 dimensions, 50 metrics) that an agent would not otherwise know, though it does not describe pagination or output shape limits.

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?

Front-loads the resource and fields, then adds the quota detail in one compact clause; nothing is redundant. The awkward line break is cosmetic and the 'Read only' clause largely duplicates the annotation.

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 output schema, the description carries the burden of explaining returns and does so by listing the returned fields and quota counts. Adequate for a simple two-parameter read tool; the client/property resolution is left entirely to the schema.

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 description coverage is 100% and both parameters (client_id, property_id) are fully documented in the schema, including fallback behavior. The description adds no parameter-level meaning, so the baseline 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?

States a specific resource (custom dimensions/metrics of a GA4 property), enumerates the fields returned, and adds quota context. It is clearly a read/list tool, which distinguishes it from the adjacent ga4_plan_custom_dimension_create sibling, though it never names that sibling explicitly.

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?

'Read only' signals the mode of use and the quota explanation implies an auditing/inspection scenario, but there is no explicit guidance on when to pick this over ga4_properties or the plan_* creation tools. Usage is only implied.

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