Get Subscriber by Email

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

Annotations already declare readOnlyHint=true and destructiveHint=false. The description adds the context of looking up by email within an audience but does not disclose behavior when subscriber not found, pagination, or any side effects. Adequate given annotations.

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?

Single concise sentence with key action and resource front-loaded. No unnecessary words, but could benefit from a bit more structure (e.g., bullet points for parameters).

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 simple read tool with existing output schema, the description is minimally complete. However, it lacks any context about prerequisites, error handling, or relationship to audience resources.

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 50%: only audience_id has a description ('Audience ID.'). The description adds that the lookup is 'by email address' but doesn't elaborate on parameter meaning, format, or constraints beyond the schema. Insufficient compensation for the half-covered parameters.

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 ('look up') and the resource ('subscriber in an audience by email address'). It distinguishes from siblings like shipmail_get_subscriber (likely by ID) and shipmail_add_subscriber.

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 on when to use this tool vs alternatives such as shipmail_get_subscriber (by ID) or shipmail_list_subscribers. Missing when-not-to-use or context.

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