Subscribe (free)

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

Beyond the annotations, the description discloses important behavior: it never starts a paid plan and is idempotent with 'Does nothing if already subscribed.' This adds meaningful context about side effects and state changes that annotations alone do not convey.

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 four short sentences with no filler. Each sentence contributes a distinct piece of information: what the tool does, what it avoids, its idempotent behavior, and when to invoke it.

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?

The tool is simple with one fully documented parameter, and the description covers the key behavioral guarantees needed for correct invocation. The absence of an output schema is acceptable because the description focuses on action semantics rather than return values.

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%, so the sole parameter 'publication' is already fully documented with examples. The description does not add parameter-level detail, but it does not need to because the schema already carries the semantic weight.

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 states a specific verb and resource: 'Free-subscribe the logged-in account to a publication.' It also distinguishes the tool from paid subscriptions and clearly differentiates it from the sibling unsubscribe tool by focusing on the act of subscribing.

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 an explicit trigger condition: 'Only use when the user explicitly asks to subscribe.' It also implies a boundary by noting that it never starts a paid plan, which helps disambiguate from paid subscription flows, though it does not explicitly name alternatives.

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