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 the delivery mechanism (signed POST to callback), the cost model (billed per address per day) and a hard constraint (callback must be public https). It omits lifecycle details such as how the subscription is cancelled or whether retries occur.

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 tight sentences, front-loaded with the core action and trigger, then rationale, then billing and the callback constraint. Every sentence adds signal; no padding.

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 subscription tool with no annotations and no output schema, the description covers purpose, trigger conditions, delivery, cost, and constraint. It leaves the subscription lifecycle (unsubscribe/response value) unaddressed, a minor gap.

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 100%, so both parameters are already documented in the schema; the description's 'callback must be public https' largely restates the schema's 'Public https URL to receive events'. Baseline 3 is appropriate since the schema does the heavy lifting.

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+resource ('Subscribe to an address') and immediately defines the trigger semantics (blacklist/sanctions/scam list). It also distinguishes itself from the one-off screening siblings by stating that a single check 'cannot warn you about a freeze that has not happened yet'.

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?

Clearly signals when to reach for this tool (continuous monitoring to catch future events) versus a one-off check, but it never names the alternative sibling (e.g. onyx_screen) or states explicit when-not conditions.

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