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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false, and openWorldHint=false, so the safety profile is fully covered. The description adds value beyond that by disclosing what the report contains (profile load state, signal counts, load errors) - effectively substituting for the missing output schema. It does not say whether load errors are blocking or how failures surface, keeping it from 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?

Two short sentences, zero filler, and the core resource identity is front-loaded before the sibling disambiguation. Every clause earns its place.

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 parameters and no output schema, the description carries the return-value burden and does so at a summary level (profiles, counts, errors). Combined with fully specified annotations, an agent has enough to call it correctly; only the shape/format of the status payload is unspecified, which is minor for a no-arg status check.

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?

The tool takes zero parameters, so there is nothing for the description to disambiguate; baseline 4 applies. No parameter claims are made or contradicted.

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 specific resource (the MECHANICAL layer's health) and enumerates the concrete contents: profiles loaded, signal counts, load errors. The second sentence explicitly distinguishes it from the hardware_ and software_ status siblings, so an agent can route correctly without opening any schema.

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 line 'One status tool per layer - the three report different layers, not the same server' tells the agent exactly which sibling to pick and why they are not interchangeable. It lacks an explicit 'do not use when' clause or a pointer to the layer-specific detail tools (mechanical_list_robots, mechanical_get_robot_signals), which is the only gap.

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