List services

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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint, destructiveHint=false, so the safety profile is covered. The description adds non-obvious context: that services are created implicitly via node advertisement and that creation is unsupported here. It does not mention pagination or result shape, but with strong annotations a 4 is warranted for the extra provisioning context.

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 sentences, all earning their place: purpose first, definition second, creation/limitation third. Slightly longer than a minimal list tool needs, but the sentences are dense and front-loaded with no filler.

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 list tool with annotations covering safety, the definition is complete: it explains the resource, its lifecycle, and the boundaries of the MCP. No output schema exists, and the description appropriately does not promise one.

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?

Parameter count is 0, so the baseline of 4 applies; there is nothing for the description to compensate for and no misleading param guidance.

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+resource ("List all Tailscale Services in your tailnet") and distinguishes from siblings by explaining what a Service is (stable MagicDNS names, virtual IPs, decoupled from devices) and naming the update/delete/approval tools rather than get_service. An agent can select this over siblings without opening other 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?

Explicitly tells the agent when services exist (created implicitly on advertise) and explicitly excludes what this MCP cannot do (no create API endpoint), redirecting to update/delete/approval tools. When-to-use and when-not-to-use are both present.

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