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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is known. The description adds valuable behavioral nuance: the id is account-relative, counts from 1, is safe to show, and is the identifier other tools expect. This goes beyond the structured fields and prevents an agent from treating the id as a global or sensitive value. No contradiction with annotations.

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?

Two sentences, zero wasted words. The primary action and filter are front-loaded in the first sentence, and the id semantics in the second sentence earn their place by preventing misinterpretation. This is an ideal size for a simple list 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?

The tool is low-complexity (one optional parameter, enums, output schema present), annotations cover safety, and the description addresses the key non-obvious behavior (id semantics). Since an output schema exists, the description does not need to list return fields. Nothing essential for correct invocation 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 description coverage is 100%: the single status parameter is fully documented with enum values and a default. The description only restates 'with status filter' without adding new parameter-level meaning. According to the baseline rule for high schema coverage, 3 is appropriate.

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?

Description states a specific verb ('List'), resource ('machines'), scope ('registered for the account'), and a modifier ('with status filter'). This clearly differentiates from the many sibling list_* tools (list_beans, list_grinders, etc.) and from mutation tools like register_machine/update_machine. The purpose is unambiguous and actionable.

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?

The description makes the use case clear: an agent should call this when it needs the account's machines, optionally filtered by status. It does not explicitly compare with alternatives or state when not to use it, but for a simple read-only list tool the context is sufficiently clear. Lacks the explicit exclusion/alternative guidance that would earn a 5.

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