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

Annotations already declare destructive=true, idempotent=false and openWorld=true, so the safety profile is covered. The description adds a genuinely useful behavioral fact not present in structured data (no signing-secret rotation), but does not explain why the call is flagged destructive (e.g. whether events replaces the whole list).

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, front-loaded with the purpose and with zero padding. The middle sentence largely repeats what the schema already shows, which is the only mild inefficiency.

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?

An output schema exists so return values need no explanation, and annotations cover the risk profile. The remaining gap is whether an events list replaces or merges with existing subscriptions, which matters for a mutation tool marked destructive.

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 webhookId and every body field. The description only restates the envelope ("webhookId + changed fields as body") and implies partial-update semantics, and it omits the enabled and settleMs fields the schema actually accepts.

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 a webhook subscription") and names the mutable facets (url, event list). It is clearly distinct from create_webhook/delete_webhook by naming, though it never explicitly contrasts them.

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?

Gives a clear condition for use (modifying an existing subscription) plus a useful exclusion: the signing secret is not rotated here, which steers the agent away from expecting rotation from this call. It does not name the alternative tool that would handle secret changes.

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