List and filter subscribers

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

Beyond the readOnly/idempotent annotations, the description discloses important behavior: the returned fields come from the publication's saved Display settings, per-request column lists are ignored, and engagement columns may be filterable but usually absent from results. It also explains the count semantics, making the tool's actual runtime behavior transparent without relying on structured hints alone.

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 dense but efficient: the first sentence states the tool's scope, the second defines the return shape and count semantics, and the third delivers a critical caveat with a pointer to the export tool. Every sentence earns its place, and the most important usage nuance is front-loaded before the alternative is mentioned.

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?

Given the tool's filtering complexity, lack of an output schema, and seven parameters, the description covers the essential gaps an agent would otherwise hit: return keys, count semantics despite limit, the Display-settings behavior, and when to switch to export_subscribers. The verbose schema handles column/operator details, so nothing important is left unexplained at the description level.

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 high at 86%, so the schema already documents most parameters thoroughly, including operators, column types, and defaults. The description adds meaningful parameter-level insight by advising limit: 1 as a cheap segment-size check and by explaining that column lists are ignored. This goes beyond the schema without needing to repeat every parameter detail.

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 opens with 'List subscribers' and specifies the exact scope: same filtering as the dashboard, 48 columns, free-text search, sorting, and paging. It clearly distinguishes itself from export_subscribers by noting that engagement values usually require that sibling tool. This is a specific verb+resource definition that an agent can act on immediately.

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 provides explicit usage guidance: 'calling with limit: 1 is a cheap way to size a segment before pulling it' and 'Use export_subscribers to read their values' for engagement columns that are filtered on but not returned. This names an alternative and states the condition under which that alternative is preferred, giving clear when-to-use and when-not-to-use signals.

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