ga4_update_key_event

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

Discloses it's a WRITE operation, the need for environment variable and confirmation, and updateMask behavior. No annotations to contradict. Could mention side effects but adequate.

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?

Very concise, front-loaded with [GA4 WRITE], no wasted words. Every sentence adds useful information.

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?

Covers essential aspects: parameters, prerequisites, updateMask logic. No output schema mentioned, but for an update tool this is acceptable.

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?

Adds value beyond schema: explains updateMask derivation, body usage for nested fields. Schema coverage is 80%, so description compensates well.

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 action ('Update a key event') and resource, with examples ('counting method or default value'). It distinguishes from sibling tools like ga4_create_key_event and ga4_delete_key_event.

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?

Provides guidance on how to use: pass only fields to change, updateMask derivation, and prerequisites (GA4_MCP_ENABLE_WRITES=true, confirm=true). Lacks explicit 'when not to use' but is sufficient.

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