LobbyStack

Update a contact

update_contact

DestructiveIdempotent

Changes a contact's details. Send only the fields to change. Set name, email, locale or timezone to null to clear them. The phone number can be changed but not cleared.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "contact_id": "<contact_id>"
    },
    "name": "update_contact"
  }
}

Input Schema

Name	Required	Description
`name`	No	Full name, or null to clear it.
`email`	No	Email address, or null to clear it.
`phone`	No	New phone number in E.164 format.
`locale`	No	Language for the contact's reminders and confirmations (en, fr, es or sr), or null to clear it.
`timezone`	No	IANA time zone, or null to clear it.
`contact_id`	Yes	The contact id (UUID).

Output Schema

Name	Required	Description
`id`	Yes	Stable identifier (UUID).
`name`	Yes
`email`	Yes
`phone`	Yes
`locale`	Yes
`passcode`	Yes	The contact's keypad PIN, which callers type to change appointments when verification_mode is passcode_required: whether there is one, never the PIN itself. null: the contact has no PIN.
`timezone`	Yes
`created_at`	Yes	ISO 8601 timestamp in UTC.
`updated_at`	Yes	ISO 8601 timestamp in UTC.

Schema Changelog

Changes observed during successful MCP inspections.

First observedNov 12, 2026

TDQS

A4/5.0

Behavior4/5

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

Annotations already declare destructiveHint=true and idempotentHint=true, so the safety bar is lowered, yet the description still explains what destruction means here: setting a field to null wipes it, while phone cannot be wiped at all. It does not mention permission requirements or what happens to omitted fields beyond the partial-update implication.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Four short sentences, front-loaded with the operation and then the three rules that matter (send only changes, null clears, phone cannot be cleared). No filler, no repetition of the title.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

The tool has an output schema, so return values need no explanation, and annotations cover the safety profile. For a six-parameter partial-update tool, the description supplies the clearing semantics and the phone exception that an agent could otherwise get wrong.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so baseline is 3, but the description adds real meaning beyond it: it consolidates the null-clearing rule across name, email, locale and timezone and calls out the exception that phone can be changed but not cleared. That exception is the single most error-prone parameter behavior and it is stated plainly.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource ("Changes a contact's details") that unambiguously separates it from create_contact, get_contact and search_contacts. It doesn't explicitly name a sibling, but the mutation-of-existing-record framing is clear enough for correct selection.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

"Send only the fields to change" gives the key partial-update rule, which is genuine when-to-use guidance. However, it never states prerequisites (e.g. the contact must already exist) or contrasts with alternatives like create_contact, so context is implied rather than explicit.

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

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