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

Beyond the annotations, it discloses the probe mechanics (one probe from Tanod's servers, no credentials, port 443, no redirects, 15 s cap), billing behavior (unresponsive servers are charged, malformed or private addresses are a 422 and not charged), pricing, rate limits, and an untrusted-output warning, none of which the annotations convey.

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?

Front-loaded with purpose and routing to siblings before logistics. It is densely packed with pricing, timing, limits, and a security note in one paragraph, which is efficient but slightly overstuffed for a single-input tool.

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?

Even though an output schema exists, the description summarizes the returned fields (name, version, protocol, sign-in, tool count and names, latency, TLS expiry, status class) and covers error semantics, timing, cost, and trust guidance. Nothing an agent needs to call it correctly is missing.

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 the schema already spells out 'host name only, port 443, no user info', so the description's 'public https URL of the MCP server endpoint' is largely redundant. The 422-for-private-address note adds a little meaning but is behavioral rather than parameter-level. Baseline 3 fits.

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 first sentence states a specific verb and resource ('Check whether a remote MCP server is up and what it offers') and explicitly contrasts itself with scan_agent_package and preflight_mcp_listing, so the agent can separate it from the closest siblings without opening a schema.

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 explicit exclusions ('It reads no code') and names two alternatives with the conditions that select them (scan a package before installing, check a repo against an awesome list). The scope is also bounded by public-only, https-only, one-probe semantics.

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