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

With no annotations provided, the description carries the full behavioral burden. It discloses pricing per mode, the requirement for a payment-signature header, the error behavior when that header is absent, and the range of replay scenarios (duplicate, out-of-order, delayed, malformed, invalid-signature). This is substantial beyond a generic tool summary, though it stops short of detailing data retention or expiration.

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 dense but efficiently structured: an opening one-line purpose, a mode-by-mode breakdown separated by semicolons, and a crisp payment/error sentence. No words are wasted, and the most important behavioral information is front-loaded.

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?

The description covers purpose, modes, and payment, but omits the concrete JSON fields needed for non-capture modes — e.g., the capture identifier for retrieve, or the target URL for replay and conformance. Given the tool's complexity and lack of output schema or annotations, an agent would still need more detail to reliably construct valid inputs for every mode.

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 schema covers the two parameters generically ('question or input' and 'optional supporting text'), but the description adds the real semantics: the 'query' parameter must contain a mode, and it enumerates the valid mode values with pricing. This meaningfully compensates for the schema's lack of mode-specific structure.

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 clearly identifies a specific resource ('disposable webhook test lab') and enumerates four distinct verbs with concrete outcomes: create a callback URL, fetch captured requests, deliver replay scenarios, and run a conformance battery. It is unambiguous and naturally distinguishes itself from the unrelated marketing/analysis sibling tools.

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 description gives clear operational context: modes are selected in the JSON input, there is a pay-per-call model, and a missing payment-signature header yields a specific error. It does not explicitly name when-not-to-use alternatives, but the mode list and payment behavior provide adequate guidance for choosing and invoking the tool.

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