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

Annotations already declare idempotentHint=true, destructiveHint=false and a non-read-only mutation, so the safety profile is covered. The description goes beyond them by disclosing partial-update semantics ('Only provided fields change') and a side effect the annotations cannot express ('Re-enabling clears the failure counter'). It does not discuss permission requirements, but the added behavioral context is genuine.

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 short sentences with no filler; the mutable-field list and the partial-update rule come first, and the delete-avoidance guidance is placed last as the corrective. Every clause carries information an agent needs.

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?

Output schema exists, so return values need no explanation, and annotations plus the full-coverage input schema carry the type and safety details. For a straightforward PATCH-style mutation the description supplies everything missing: partial-update behavior, the re-enable side effect, and the alternative to deletion.

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 per-parameter baseline is 3. The description adds a cross-cutting semantic rule that the schema does not state — omitted fields are left untouched, so providing events replaces rather than merges — which materially changes how an agent should fill 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?

Names a specific verb (change/update) plus the resource (webhook endpoint) and enumerates the mutable fields (url, events, account_ids, description, is_active), so it is immediately distinguishable from create_webhook_endpoint, delete_webhook_endpoint, list_webhook_endpoints and test_webhook_endpoint among siblings.

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 states when to use it ('to change events, accounts or url, or to re-enable an endpoint disabled after failures') and gives an explicit alternative for the adjacent case ('to stop deliveries temporarily set is_active=false rather than deleting'). It routes the agent away from delete_webhook_endpoint, which is exactly the confusion risk here.

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