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

With no annotations supplied, the description carries the full burden and does so well: it states the probe is unpaid, that it 'Never pays the target', that it is a single probe, what states come back, that latency is included, and it distinguishes the free AYNE playzone from the $0.001 production endpoint. Side effects, cost behavior, and result shape are all disclosed.

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 core purpose and the 'never pays' guarantee are front-loaded, and the outcome list is compact. The trailing parenthetical about AYNE versus the production endpoint and vendor attribution is slightly noisy but still conveys real cost context, so it mostly 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?

There is no output schema, so enumerating the possible result states and mentioning latency is what makes the return values interpretable, and the description does that. It stops short of describing the response structure (field names, whether latency is a number or string), leaving a small gap for a tool whose whole value is its diagnostic output.

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% and both parameters already carry descriptions, so the description only restates that a URL is probed and that a method is expected. It adds no syntax, format, or validation guidance (e.g. scheme requirements, timeouts) beyond the schema, which is the baseline 3 case.

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 names a specific verb and resource ('Proof-of-Life: is this API/endpoint answering right now') and enumerates the exact outcome states it returns (up, paywalled, auth_required, not_found, wrong_method, degraded, tls_error, down). That is far more discriminating than the bare name 'alive' and lets an agent separate it from cost/pricing siblings like cost_estimate.

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 gives a clear trigger condition: probe 'before you spend money calling it', i.e. a pre-flight check ahead of a paid call. It does not explicitly name an alternative tool or state when not to use it, which keeps it below a 5, but the intended moment of use is unambiguous.

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