Plan a GA4 custom dimension

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

Goes well beyond the annotations: it warns that parameterName and scope are immutable, quantifies the quota (50 event / 25 user / 10 item), and discloses that no automatic rollback exists because archiving is not offered. That is exactly the kind of irreversible-consequence context an agent cannot get from readOnlyHint/destructiveHint alone, and it is consistent with readOnlyHint=true since nothing is written.

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?

Four short clauses, front-loaded with the plan-vs-write distinction, then the risk warning, then the apply step. Every sentence carries distinct decision-relevant information with no padding.

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 7-parameter mutation-planning tool with no output schema, it covers the workflow handoff, irreversibility, and quota limits, and the schema handles client/property selection. It could note how the resulting plan is retrieved (plan_get) or reviewed, but nothing essential 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?

Schema description coverage is 100% and the schema already labels scope and parameter_name as 'can never be changed later', so the description largely restates parameter facts. Its genuinely additive detail (the 50/25/10 quota) is not per-parameter guidance, so the baseline 3 is right.

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 verb (plan/register), resource (custom dimension), and target (client's GA4 property), and the 'PLAN (nothing is written)' prefix instantly separates it from apply-style siblings like google_apply and from the read-only ga4_custom_definitions.

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?

Explicitly names the follow-up action and precondition: 'Apply with google_apply after the user agreed.' That is clear workflow routing, though it stops short of stating when *not* to use this tool or what alternative exists if the user declines.

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