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

The readOnlyHint annotation already declares this is a safe read. The description only restates the read via 'Get' and adds the raw HTTP endpoint path, which is not a behavioral trait (no auth needs, rate limits, error behavior, or side effects disclosed). It adds essentially no behavioral context beyond the annotation.

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 tight sentences, front-loaded with the action and resource. The second sentence (endpoint path) is largely technical garnish for an agent and doesn't earn its place as strongly as the first, but nothing is bloated.

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 two-parameter read with full schema coverage and a readOnly hint, the description is adequate. However, there is no output schema, and the description never indicates what subscriber data (email, status, custom fields) comes back, leaving an agent without return-shape expectations.

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%: both subscriber_id and mailing_list_id are documented as GUIDs, with mailing_list_id even pointing to moosend_list_mailing_lists. The description adds no param-level meaning beyond what the schema already provides, so the baseline 3 applies.

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 (Get), resource (subscriber), and scope (one subscriber by subscriber ID within a mailing list). This implicitly distinguishes it from siblings like moosend_get_subscriber_by_email and moosend_list_subscribers, but it never names or contrasts those alternatives explicitly.

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?

The description says what the tool does but gives no guidance on when to choose it over moosend_get_subscriber_by_email (when you only have an email) or moosend_list_subscribers (when you want multiple). There are no prerequisites, exclusions, or alternative-routing instructions.

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