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

Annotations already declare readOnly, idempotent, and non-destructive behavior. The description adds substantial behavioral context beyond that: it performs a real MCP initialize handshake, measures p50/p95 latency, counts tools, hashes the tool schema for drift detection, checks RFC 9728 auth metadata, and returns error detail when dead. This fully discloses what happens when the tool is invoked.

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 front-loaded with the core purpose, then supplies behavior, return values, usage, and arguments in a clear, organized structure. It is dense but every sentence earns its place; there is no filler or redundancy.

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 two-parameter probe tool with no output schema, the description is complete: it covers what the tool does, when to use it, how it behaves, what it returns, and what each argument means. The only minor ambiguity is that p95 latency is mentioned as measured but not listed in the return fields, but the explicit return list resolves most agent uncertainty.

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 description coverage is 0%, so the description carries the full burden for explaining parameters. It does this well: url is described as the MCP/HTTP-402 endpoint URL with an example, and timeout is described with units and default value. Both parameters receive meaningful semantic context beyond the raw schema.

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 opens with a specific verb and resource: 'Probe an MCP or HTTP-402 endpoint now and get its trust verdict.' It then details exactly what the probe does (initialize handshake, latency, tool count, schema hash, auth metadata), clearly distinguishing it from monitoring or alerting siblings.

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?

Provides explicit usage guidance: 'Use before wiring any new MCP server into your client.' The 'not a ping' clarification also prevents misuse. It does not explicitly name sibling alternatives or contraindications, but the stated use case is unambiguous.

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