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

Annotations already declare readOnlyHint=true, so the safety profile is covered. The description goes beyond that by disclosing the return structure (a domain → nameserver map) and the underlying REST endpoint, which is genuinely useful given there is no output schema. It does not mention auth requirements or tailnet scoping rules.

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 compact clauses: the purpose/return shape is front-loaded, and the REST endpoint reference is tucked behind an em dash. Every element earns its place with no redundancy.

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 zero-parameter, read-only tool with no output schema, the description supplies the essential missing piece — what the return value looks like — plus an endpoint reference. Only minor details (auth scope, empty-config behavior) are absent.

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. The description has no parameters to explain and correctly does not pad the text with parameter commentary.

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 ('Get') and a precise resource ('the tailnet's split-DNS configuration'), then clarifies the return shape as a domain → nameservers map. This distinguishes it from siblings like get_dns_preferences, list_dns_nameservers, and list_dns_searchpaths without ambiguity.

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?

Usage is implied by the resource name — an agent will read this when it needs the split-DNS config — but the description never states when to prefer it over get_dns_preferences or the list_dns_* siblings, nor does it mention prerequisites or exclusions.

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