update-subscription

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

Annotations indicate destructiveHint=true, consistent with the description. Adds context about variable max extension and the need to call before expiration. Doesn't detail side effects or permissions, but annotations already signal mutation.

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 paragraphs plus a tip; front-loaded with purpose. The tip is useful, though some information (e.g., 'See subscription for maximum length') could be condensed. Not verbose.

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?

Covers the core renewal action and timing, but lacks details on response format, error handling, or permissions. With no output schema and 5 parameters (nested body), more completeness would be beneficial.

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 80% (high), so baseline is 3. The description highlights the critical parameter expirationDateTime and its ISO 8601 format, but omits details on other body fields. Adds marginal value over the schema.

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 action ('Renew a subscription by extending its expiry time') and resource ('subscription'), differentiating it from siblings like create-subscription, delete-subscription, and reauthorize-subscription.

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?

Explicitly advises to renew 'well in advance of their expiry date' and warns about missing notifications. Mentions checking max extension per resource type, but does not contrast with alternatives (e.g., reauthorize-subscription) or specify when not to use.

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