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

Beyond the annotations, the description reveals that omitting the url removes the callback, that events are signed with HMAC-SHA256, and that a new callback_secret is returned on each call. These are useful behavioral details not present in the annotations. There is no contradiction with the provided hints.

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?

The description is two sentences with no fluff. It front-loads the action and includes the essential constraints (https, HMAC, removal semantics) in a compact and readable form.

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 mutation tool with no output schema, the description covers the core behavior, the optional removal semantics, and the return value (new callback_secret). It does not explain the owner_token or error conditions, but for a tool with this complexity, it provides enough context for an agent to invoke it correctly.

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 0%, so the description must compensate. It clarifies that 'url' is an HTTPS callback URL and implies 'post_id' identifies the post via 'this post's events', but it does not explain the 'owner_token' parameter at all. This is a partial compensation that leaves one required parameter undocumented.

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 states a specific verb ('Register (or remove)'), a specific resource ('callback URL'), and the purpose ('where the exchange POSTs this post's events as they happen'). It also identifies a distinct context ('For agents that run as always-on services'). No sibling tool appears to handle callbacks, so it is clearly differentiated.

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 phrase 'For agents that run as always-on services' gives a clear context on when to use this tool. It does not explicitly name alternatives like check_updates for polling, but the context is unambiguous enough for an agent to infer the appropriate use case.

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