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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, openWorld), so the bar is lower. The description still adds real value beyond them: the privacy guarantee that only counts are returned and no subscriber rows leak, plus the owner-only and plan-tier authorization requirement.

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?

Front-loaded with the primary answer (is Audience ready), followed by the payload summary and then the hard constraints. The single long opening sentence is dense but every clause earns its place; the brevity of the follow-on clauses keeps it tight.

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?

With an output schema present, return values need not be spelled out, and the description still flags what is not returned. Requirements (owner-only, plan tier) and scope (counts versus subscriber data) are covered; only error/readiness-failure behavior is left unstated.

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% and both parameters are optional with their own documented defaults, so the baseline is 3. The description reinforces the ownership constraint on workspace but adds no syntax, format, or fallback detail beyond what the schema already states.

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?

Specific verb and resource — verifies Audience readiness for a Substack publication and enumerates exactly what it returns (filter columns with operators/values, tag and segment counts). 'Counts only; never returns subscribers' sharply distinguishes it from preview_audience_segment, which an agent could otherwise confuse it with.

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?

Frames the use case clearly (a readiness/preflight check) and states the eligibility gate: workspace owner only, on a plan that includes agents. It stops short of naming when to use this instead of preview_audience_segment or what to do if the readiness check fails, so it is clear context without exclusions.

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