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

With no annotations provided, the description carries full behavioral disclosure burden and does so exceptionally. It reveals the gating rule, the hard denial for non-subscribers, the deliberate anti-disclosure rationale, and the indistinguishable error behavior across zero/many/nonexistent tags.

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 every sentence earns its place. The core behavior is front-loaded, the gating rule is highlighted, the rationale is compactly explained, and the return payload is stated at the end without redundancy.

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 no output schema, the description still specifies the return fields: account_id, org, and subscribed_at. It also covers error semantics and authorization requirements, making the tool fully callable and interpretable by 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?

The description clarifies that `tag` is the tag whose subscribers are listed, adding meaning beyond the schema's bare `tag` string field. The optional `owner_key` parameter is already fully documented in the schema, so the description need not repeat it.

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 a concrete verb-resource pair: 'List every account currently subscribed to `tag`.' This clearly identifies the tool's purpose and distinguishes it from tag-adjacent siblings like list_by_tag by specifying the exact resource being listed (subscriber accounts).

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 call-time context: the caller must themselves be a subscriber, and non-subscribers receive a hard denial. It does not explicitly name alternative tools to use when conditions are not met, but the gating precondition is unambiguous and actionable.

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