Set contacts

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

Annotations declare the safety profile (readOnlyHint=false, idempotentHint=true, destructiveHint=false), but the description goes well beyond them: it discloses PATCH semantics per contact type, parallel execution, per-type error isolation, and the exact partial-failure response shape (data: { applied, failed }) with instructions to inspect data.failed. This is non-obvious behavior an agent could not infer from structured fields.

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 tight sentences, front-loaded with the action and then the failure-mode contract. No filler, and the most decision-relevant fact (partial failures are preserved) is stated before the response details.

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 output schema, the description correctly documents the failure response, which is the highest-value gap to fill. It omits the success-path response shape and any note on omitted contact types being left unchanged, but it is otherwise sufficient for a 3-optional-param mutation tool.

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% and each nested property already documents its email and validation pattern, so the schema carries the parameter burden. The description only restates the three contact type names, adding no format or merge/replace detail beyond the schema — the expected baseline of 3.

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: 'Update tailnet contact information', and names the three contact types (account/support/security) that can be set. It is clear what the tool does, but it never distinguishes itself from siblings like tailscale_get_contacts or tailscale_resend_contact_verification, so an agent gets no explicit routing signal.

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?

There is no when-to-use or when-not-to-use guidance, and no mention of the read-side sibling (tailscale_get_contacts) or prerequisites such as admin/tailnet-owner scope. Usage is only implied by the verb 'Update'.

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