is_site_up

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

With no annotations, the description carries the full burden, and it does disclose two genuinely useful traits the schema cannot: that the result is a live/point-in-time check and that the call is Paid. It also names the return fields (http_status, reachable, latency_ms), which is helpful given there is no output schema. It does not disclose timeouts, redirect handling, or behavior on malformed URLs.

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?

Three short sentences, front-loaded with the core question, then cost, then return shape. Every clause carries information and nothing is padded.

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 simple one-parameter read tool with no annotations and no output schema, the description covers purpose, cost, and the fields returned, which is most of what an agent needs. Minor gaps remain around timeout/error semantics and explicit contrast with check_domain, but the core affordances are present.

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?

There is a single parameter with 100% schema description coverage ('Full URL to check'), so the schema already does the work. The description adds nothing about URL format, scheme requirements, or protocol support, making the baseline 3 appropriate.

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 states a specific check verb and resource: whether a given URL is up or down right now. It is distinguishable from siblings like check_domain and summarize_url by being a real-time reachability probe. It stops short of explicitly naming the sibling it contrasts with, so it lands at 4 rather than 5.

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?

There is no guidance on when to use this instead of check_domain, summarize_url, or the other siblings, and no exclusions or prerequisites. The only implicit context is 'right now', which hints at live probing versus historical data, but that is inference rather than stated guidance.

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