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

With no annotations, the description carries the full burden and does well: it discloses that a challenge POST may be sent, that frequency is capped at one message per update, that every message carries an unsubscribe link, and that no API key is needed. It stops short of describing the success response or any failure/rejection behavior.

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?

Four tightly packed sentences with no filler, and the core action plus delivery target are front-loaded. The parenthetical mechanism explanations are dense but each earns its place.

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 3-param tool with no annotations and no output schema, the description covers opt-in, transport, verification, rate caps, unsubscribe, and auth. The main omission is whether a confirmation handshake is expected before the subscription becomes active.

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 coverage is only 33% (only url is documented), but the description compensates by explaining the semantics of both enum parameters: verify=echo vs verify=well_known, and webhook vs A2A endpoint for kind. This adds real meaning beyond the bare enum values.

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 ('opt in to') and resource ('Haven update notices') with the delivery target (webhook URL or A2A endpoint). It is clearly distinguishable from siblings like unsubscribe_updates, though it never names that inverse tool explicitly.

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 concrete selection guidance between the two verification modes (echo vs well_known), explaining the mechanism of each. It does not mention whether a separate confirmation step (e.g. confirm_subscription) is required, leaving a gap on the overall flow.

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