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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description adds value by enumerating the exact return fields (id, type, params, created_at, last_fired_at, fire_count), which helps the agent understand what to expect without an output schema. It does not mention pagination or ordering, but this is a minor omission for a simple list tool.

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 extremely concise—two sentences—with information front-loaded. It covers purpose, return format, and usage in a highly efficient manner, with zero fluff or 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?

For a read-only list tool with one optional parameter and no output schema, the description is complete. It states what the tool does, what it returns, and when to use it. The context signals confirm low complexity, so no additional details are necessary.

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 a single optional parameter (include_inactive) that already has a descriptive comment and default value. The description adds no additional parameter semantics beyond what the schema provides, so 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 opens with 'List the caller's active subscriptions', which uses a specific verb ('List') and a clearly defined resource ('the caller's active subscriptions'). This distinctly differentiates it from sibling tools like subscribe and unsubscribe, which perform different actions on subscriptions.

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 second sentence explicitly states when to use this tool: 'Use this to review what you're monitoring before adding more or to find an id to cancel.' This gives clear contextual guidance and implicitly points to alternatives (subscribe/unsubscribe) without needing to name them.

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