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

No annotations are provided, so the description carries the full burden. It discloses the mechanism (calls every endpoint hourly), the uptime calculation nuance (never counting unmeasured hours as down), the paid/free distinction, and the output fields. It doesn't mention side effects or auth, but as a status check it's implicitly read-only. The disclosure is strong but lacks explicit error-handling details.

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 verbose and somewhat rambling, starting with a rhetorical question and then covering the watchtower mechanism, output details, usage guidance, and pricing in a single block. It's informative but could be structured more clearly with sections or bullet points. It earns a 3 because it's not overly terse but could be better organized.

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?

Given there is no output schema, the description must explain the return value, and it does: it lists status categories, uptime, response time, payment info, and fixes. It also covers both invocation modes and mentions the paid endpoint for full history. However, it doesn't specify what happens if an agentId is invalid or the response format details, but for a status tool this is reasonably complete.

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 the baseline is 3. The description adds significant value beyond the schema by explaining the effect of including vs. omitting agentId (specific status vs. whole-registry counts) and the exact meaning of the parameter. This goes beyond a simple description of the field.

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 states it checks whether an Arc agent actually answers, providing status, uptime, response time, payment info, and fixes. It distinguishes between the with-agentId and without-agentId modes, and none of the sibling tools address agent health, so it's uniquely identifiable.

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 explicitly says 'Call it before you pay or hire an agent,' providing a clear use case. It also explains the two invocation modes (with and without agentId) and mentions the paid endpoint for full history. However, it doesn't explicitly state when not to use it or name alternatives, though no direct sibling competitors exist.

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