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

Annotations already declare destructiveHint=true and openWorldHint=true, so the safety profile is partly covered, but the description adds real value by flagging an authorization requirement and that only the "owned" subscription is affected. It does not explain consequences for fields omitted from a call, which is the main remaining gap.

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?

Three tightly packed sentences with the trigger condition front-loaded and no filler. Slightly dense/telegraphic at the end ("use list-webhook-events for valid keys"), but every sentence carries information.

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 5-parameter mutation tool with no output schema, the description covers trigger, prerequisites, authorization, and external side effects. Given annotations carry the destructive/open-world profile, what remains missing (merge-vs-replace semantics for nested metadata, error behavior) is minor.

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 baseline is 3; the description goes beyond it by telling the agent where parameter values must be sourced (subscription_id from list-webhook-subscriptions, events from list-webhook-events). It restates the field list rather than adding format detail, so it stops short of a 5.

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 names a specific verb (updates) and resource (owned webhook subscription) and enumerates exactly what can be changed: endpoint URL, subscribed events, active status, metadata. It is clearly distinguishable from create-/delete-/list-webhook-subscription siblings, though it never explicitly states what it is not for.

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?

Opens with an explicit trigger condition ("Use this when the user wants to change...") and names prerequisites, stating subscription_id must come from list-webhook-subscriptions and event keys from list-webhook-events. No explicit when-not guidance, but the context is clear enough to route correctly.

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