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

With no annotations, the description carries the behavioral burden and does disclose real traits beyond the schema: the shape of the returned payload and, importantly, that ambiguous inputs produce a `matches` list ordered most-likely-first. That ambiguity handling is exactly the kind of behavior an agent cannot infer. It omits error behavior when nothing matches and does not state precedence among name/url/package.

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 most useful information (what you get back) is front-loaded, followed by the lookup-key options. Two sentences, no filler. The second sentence is dense with three distinct ideas but remains parseable.

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?

There is no output schema and no annotations, so the description must cover return shape and safety; it covers return shape adequately. However, with four optional parameters and no required key, an agent still cannot tell the precedence among name/url/package or what happens when nothing matches. Those are material gaps for a lookup tool whose main failure mode is an ambiguous or empty result.

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 75%, just under the threshold where the schema would do all the work. The description adds genuine meaning beyond the schema fields: it explains why url or package is acceptable (to resolve the registry name) and ties the undocumented `runtime` parameter to install-snippet selection. It leaves the runtime enum values themselves uninterpreted.

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 uses a specific verb and resource ('Full details for one entry') and enumerates the payload: raw server.json, install snippets, lookupd metadata. It also distinguishes the lookup modes (registry name vs. url/package), which separates it from find_capability and health. It does not explicitly name those siblings, so it falls just short of a 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?

It gives clear positive guidance on which key to pass depending on what the agent has: a registry name, or a remote url / npm/PyPI package from an existing MCP config. It even explains the downstream purpose ('that finds the registry name to use with report_outcome'). It stops short of explicit when-not-to-use or precedence rules among the three keys.

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