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

Annotations already declare readOnly, idempotent, closed-world and non-destructive, so the safety profile is covered. The description adds value beyond them by disclosing the auth requirement (plan must include printing) and by defining the semantic scope of 'printer' as devices reachable via a paired agent, which affects what an agent should expect in the result.

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 short sentences, zero waste, with the scope definition front-loaded and the downstream usage and prerequisite following in dependency order. Nothing is repeated from the title or annotations.

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 name the key returned field (`id`) plus a requirement for calling the tool. It does not describe what else a printer record contains (name, status, agent state), so an agent knows how to chain the call but not the full shape of 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?

The tool takes zero parameters, so the baseline is 4 and there is nothing the description needs to compensate for. It instead spends its words on the return-value linkage (device `id` feeding print_label), which is the useful information here.

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 verb and resource ('List the printers registered to the Labelixa account') and immediately disambiguates scope with the parenthetical explaining these are the devices a paired DirectPrint agent forwards jobs to. An agent can distinguish this from sibling listing tools like template_list or bulk_list without opening either 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?

Gives explicit downstream routing: the returned device `id` is what you pass as `device_id` to print_label, which tells the agent exactly why and when to call this. It also names a prerequisite (API key plan including printing). It stops short of stating exclusions, but there is no sibling that competes for this job, so little is left to inference.

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