Trust host key

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

Annotations already declare destructiveHint=true and idempotentHint=true, but the description adds real context beyond them: which file is mutated (known_hosts), that existing entries are replaced, and the edge case that a host returning no keys leaves the file untouched. It doesn't discuss permissions or side effects on other host entries, so not a 5.

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?

Core action is front-loaded in sentence one, followed by tightly-scoped behavior notes with no filler. The parenthetical and multi-clause sentences are slightly dense but each clause carries usable information.

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 one-parameter mutation tool with an output schema and annotations covering safety traits, the description covers the remaining gaps an agent needs: what is modified, replacement semantics, and the no-op edge case. Nothing needed to invoke 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 single parameter has a detailed description covering both alias and hostname/IP forms. The description adds only the ssh-keyscan connection detail, so this is the baseline 3 where the schema does the heavy lifting.

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?

States a concrete verb + resource + implementation: 'Fetch a host's keys (ssh-keyscan) and add them to known_hosts.' It also positions itself against a sibling by calling itself 'the inverse of forget_host', so an agent can distinguish it from add_host/forget_host without opening schemas.

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?

Gives a clear usage context (afterwards a non-interactive ssh won't stop on the trust prompt) and names the inverse operation forget_host, plus the re-run-safe case. It stops short of explicit when-not guidance and doesn't distinguish itself from the sibling add_host, which could plausibly perform a similar trust action.

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