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

Annotations already declare destructiveHint=true, idempotentHint=true, openWorldHint=true, and readOnlyHint=false, so the safety profile is carried by structured data. The description adds the entitlement requirement (Pro or Builder), which is genuinely new information, but it does not explain why an update is flagged destructive — namely that the events array replaces the existing subscription list — nor whether omitted fields are left untouched.

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 with no filler: the operation and its mutable fields come first, and the entitlement constraint follows. Every clause carries information an agent needs before calling.

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 five-parameter, single-required-field update tool with full schema coverage and no output schema, the description covers purpose, mutable fields, and plan gating adequately. The notable remaining gap is partial-update semantics — whether unspecified fields are preserved — which matters for a mutation tool but is partly inferable from the phrasing.

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 the schema already documents every parameter, including the full event-type enumeration. The description merely mirrors the field list without adding format, validation, or partial-update semantics beyond what the schema provides; baseline 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?

States a specific verb and resource ('Update an existing webhook endpoint') and enumerates the mutable fields (URL, subscribed events, display name, enabled status), which distinguishes it from create_webhook, delete_webhook, and list_webhooks in the sibling set. It stops short of explicitly naming those siblings, but the operation is unambiguous.

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 tool's usage is implied by the phrase 'Update an existing webhook endpoint' plus the plan prerequisite 'Requires Pro or Builder', which is useful gating context. However, there is no explicit guidance on when to choose this over test_webhook or delete_webhook, and no statement of what happens if a non-entitled account calls it.

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