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

Annotations already declare a read-only, idempotent, closed-world call, and the description adds substantial context beyond them: test statuses returned, tool counts, latency and timestamp, result ordering, exclusion of servers with agent-directed descriptions, and an explicit third-party-data warning. This is exactly the behavioral context an agent needs before invoking.

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 sentences, front-loaded with what the tool does, then result contents, then ordering/filtering and the safety warning. Every sentence carries information; the result-field enumeration is dense but earns its place since no output schema exists.

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?

With no output schema, the description fully compensates by explaining what each result contains (test outcome, tool count, speed, timing, address). Combined with annotations, an agent has everything needed to decide to call and interpret the response.

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 80%, with enums documenting level, category, and language, so the baseline is 3. The description adds no parameter-level detail such as how query matches or how limit interacts with ordering; its prose about result fields describes returns, not inputs.

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 gives a specific verb and resource: find remote MCP servers from the official MCP Registry that Horizontal connected to and tested. Scope (tested servers only, third-party data) is precise. It does not name or differentiate from the sibling get_service, so it falls short of 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?

Usage is implied: search for servers, working ones come first, and read third-party warnings before connecting. There is no explicit statement of when to use this versus get_service, nor any when-not guidance; the level parameter's filtering intent is only hinted at in the schema.

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