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

Annotations already declare readOnlyHint=false and openWorldHint=true, so mutation and external exposure are covered. The description adds genuinely non-obvious behavior: payloads are signed POSTs, the HMAC secret is returned only once ('once'), and the signature header is X-Alion-Signature — all facts an agent could not derive from structure. It stops short of saying what happens to an existing webhook when a new URL is set (replace vs. error).

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?

One dense paragraph with no filler; the event list, the secret-shown-once caveat, the removal sentinel, and the docs link all earn their place. It is slightly parameter-first rather than action-first, which delays the key 'this sets a webhook' framing by a few 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?

For a one-parameter mutation with no output schema, the description is nearly self-sufficient: it covers the input contract, the return value (secret returned once), and the removal path. What remains unstated is replacement semantics when a webhook already exists and how to rotate the secret without losing it.

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 single 'url' parameter has zero schema description coverage, so the description must carry it — and it does: it specifies 'public https', ties the parameter to what will be delivered, and defines the sentinel value (empty string removes the webhook). Missing only format/length edge cases to reach 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 conveys that this tool registers a public HTTPS URL to receive agent events, and that an empty URL deregisters it, so the underlying action is inferable despite never using an explicit verb like 'set'. It clearly belongs to a different domain than every sibling (search/agent_status/conversation tools), so no ambiguity arises.

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?

It enumerates the exact event types the webhook will receive, which implies when to use it (push-based delivery of message/agent events), and it explicitly documents the removal case: 'Pass an empty url to remove it.' However, it never contrasts with pull-based siblings like get_conversation or list_conversations, and gives no prerequisites beyond 'public https'.

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