ga4_update_custom_dimension

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

The description discloses it's a write operation and the immutability constraints, but does not discuss side effects, rate limits, or detailed behavior beyond what is obvious from the name.

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 concise sentences with a clear front-loaded "[GA4 WRITE]" indicator and no superfluous text.

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 an update tool with 6 parameters and no annotations, it covers purpose, immutability, usage of updateMask, and prerequisites, but lacks information about return value or error handling.

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 50%; the description adds value by explaining updateMask derivation and that only fields to change need be passed, but does not clarify specific modifiable fields beyond what the schema lists.

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 clearly states the tool updates a custom dimension and explicitly mentions that parameterName and scope are immutable, distinguishing it from create and archive siblings.

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?

It explains that updateMask can be derived from supplied fields and requires GA4_MCP_ENABLE_WRITES=true and confirm=true, but could explicitly state when to use this vs. create or archive.

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