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

Annotations already declare readOnlyHint true and destructiveHint false, so the safety profile is covered. The description adds the list of return fields and clarifies the scope ('caller's active subscriptions'), providing useful context beyond annotations. It does not mention the include_inactive parameter behavior, but that is captured in the schema.

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, front-loaded with the purpose, then return fields, then usage context. Every sentence serves a distinct purpose with no unnecessary detail.

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 the tool's simplicity (one optional param, no output schema, strong annotations), the description is sufficiently complete. It covers purpose, return fields, and usage. The only minor gap is the lack of mention of include_inactive, but that is adequately documented in the schema.

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 the single optional parameter include_inactive is fully described in the schema. The description does not add any additional meaning or syntax beyond the schema, so the baseline of 3 applies.

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 the tool lists the caller's active subscriptions, with a specific verb 'List' and resource 'subscriptions'. It also enumerates the returned fields, distinguishing it from siblings like subscribe and unsubscribe which perform mutations.

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?

Explicit guidance is given: 'Use this to review what you're monitoring before adding more or to find an id to cancel.' This tells the agent when to use it relative to subscribe/unsubscribe, though it does not explicitly name alternative tools or state when not to use it.

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