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

Beyond the annotations (which only flag a mutating, idempotent, open-world call), the description supplies delivery semantics (retries), expected latency (~1 minute), the scoping guarantee that existing destinations are unaffected, and the one-time disclosure of the signing secret. That is exactly the kind of operational context an agent cannot get from readOnlyHint/destructiveHint/idempotentHint alone.

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 tight sentences with the primary action and the side-effect guarantee front-loaded, followed by the important one-time-secret caveat. Every clause carries information; nothing is padded or repeated.

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 two-parameter mutation with no output schema, it covers behavior, latency, idempotency, and the key return value (signing secret, shown once). It leaves minor gaps — the rest of the response shape and any error conditions (invalid URL, unknown appSlug) — but nothing that would cause an agent to call it incorrectly.

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 both parameters are already documented, and the description mostly restates that the URL is the forwarding target. It adds only modest framing — that events arrive as POSTs with retries and that the receiving server verifies via the AnyHook-Signature header — which is useful but not format or constraint detail beyond 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?

The description opens with a specific verb and resource ("Add a destination to an existing app") and immediately states the effect ("new events are forwarded to this URL"). No sibling tool adds destinations, so the unique resource alone distinguishes it from anyhook_events, anyhook_replay, and the app-management 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?

It establishes the operating context clearly: it targets an existing app, it leaves other destinations untouched, and re-adding an existing URL is a no-op. It stops short of naming when to prefer another tool or any prerequisites (e.g., plan limits, app existence), so it is strong context without explicit alternatives.

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