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

Beyond the annotations (readOnlyHint=false, destructiveHint=false), the description discloses validation specifics (https-only, <=2048 chars, URL safety blocklist), the return payload ('Returns the updated endpoint'), and that the secret is never returned. These details provide meaningful behavioral context beyond what annotations offer.

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 three concise sentences, each earning its place: the first states the core action and fields, the second states the constraint and validation, and the third states the return value and points to an alternative. No redundant words.

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 complexity (4 parameters, one required) and existing annotations, the description covers all essential aspects: which fields can be updated, the at-least-one constraint, validation rules, return behavior, and the secret alternative. With no output schema, this is sufficient for correct invocation.

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?

The input schema already provides 100% coverage with detailed descriptions for all parameters. The description adds critical semantics not present in the schema: the rule that at least one of url/events/active must be provided, and that validation mirrors register_webhook. This elevates it beyond the schema baseline.

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 starts with 'Update one or more mutable fields on a registered webhook endpoint: url, events, active.' This clearly specifies the action (update) and the resource (webhook endpoint). It also distinguishes from siblings by noting 'secret is never returned by this tool - use rotate_webhook_secret for that' and implying register_webhook validation context.

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?

Provides the critical constraint 'At least one of these must be provided' and references register_webhook for validation rules, which helps the agent decide when to apply this tool. It explicitly points to rotate_webhook_secret for secret rotation. However, it does not contrast with delete_webhook or test_webhook_delivery, so the when-not-to-use guidance is incomplete.

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