cm_update_subscriber

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

Annotations provide idempotentHint: true, but the description adds little beyond that. It does not detail what happens if the subscriber does not exist, or how changing the email field affects identification. The behavioral context is minimal, but annotations already supply some safety guarantees.

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?

The description is a single, front-loaded sentence with the verb and resource immediately visible. It is concise with no superfluous information, making it easy to scan.

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 mutation tool with no output schema, the description is adequate but lacks details on return values, error handling, or required parameters beyond what the schema provides. It reasonably covers identification but misses contextual completeness for an agent.

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 89%, so the schema already documents most parameters well. The description adds no extra meaning beyond stating that the subscriber is identified by current email, which is already in the schema. Thus, baseline 3 is appropriate.

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 verb 'Update' and the resource 'existing subscriber's details', with the method of identification 'by current email'. This effectively distinguishes it from sibling tools like cm_add_subscriber (create) or cm_delete_subscriber (delete).

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?

No guidance is provided on when to use this tool versus alternatives. For example, it does not mention that this tool should only be used for existing subscribers (and not for new ones, which would use cm_add_subscriber). The description lacks any contextual notes on prerequisites or exclusions.

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