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

With readOnlyHint, openWorldHint, idempotentHint, and destructiveHint annotations already covering safety and side effects, the description adds value by specifying the scope (caller's active subscriptions), the return fields, and the default behavior (active only). It does not disclose potential limitations like pagination, but annotations lower the bar.

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 sentences pack purpose, return fields, and usage guidance without any wasted words. The structure front-loads the action and follows with relevant context, making it easy to scan.

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 list tool with one optional parameter, the description is complete: it lists return fields, specifies scope, and gives usage guidance. Since there is no output schema, the description adequately carries the return value information. No significant gaps.

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 coverage is 100% with the parameter include_inactive clearly described ('Include cancelled subscriptions in the response (default false)'). The description's mention of 'active subscriptions' and 'cancel' slightly hints at the parameter but doesn't add meaningful detail beyond the schema. Baseline 3 is appropriate.

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 clearly states it lists the caller's active subscriptions, enumerates the return fields (id, type, params, created_at, last_fired_at, fire_count), and distinguishes it from sibling tools like subscribe and unsubscribe. The verb+resource is specific and unambiguous.

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 scenarios: 'Use this to review what you're monitoring before adding more or to find an id to cancel.' This gives clear context, but it doesn't mention when not to use or name alternatives. It's well-directed but lacks exclusions.

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