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ServiceNow CMDB MCP Server

by ketiil

preview_ci_update

Read-onlyIdempotent

Preview changes to a CI record by computing a diff against proposed field updates. Returns a confirmation token valid for 5 minutes to later confirm the update.

Instructions

Preview changes to an existing CI before applying them.

Fetches the current record, computes a diff against the proposed changes, and returns a confirmation token. No changes are made to ServiceNow.

The confirmation token is valid for 5 minutes. Pass it to confirm_ci_update to execute the change.

Prerequisites: Use search_cis or get_ci_details to find the CI sys_id first.

Typical workflow: preview_ci_update → review diff → confirm_ci_update

Examples: preview_ci_update(sys_id="abc123...", table="cmdb_ci_server", fields={ "operational_status": "6" }) # Retire a server preview_ci_update(sys_id="abc123...", table="cmdb_ci_server", fields={ "ip_address": "10.0.2.10", "short_description": "Moved to new subnet" }) preview_ci_update(sys_id="abc123...", table="cmdb_ci_linux_server", fields={ "install_status": "7", "operational_status": "2" }) # Mark as decommissioned

Args: sys_id: The sys_id of the CI to update. table: The CMDB table (e.g. cmdb_ci_server). Must be the specific class table. fields: Dictionary of field names to new values. Example: {"operational_status": "2", "install_status": "7"}. System fields (sys_id, sys_created_on, etc.) cannot be set.

Returns: JSON object with "token" (confirmation token), "sys_id", "table", "diff" (list of field changes with old/new values), and "fields" (proposed values).

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
sys_idYes
tableYes
fieldsYes

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
resultYes
Behavior5/5

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

Reinforces annotations (no changes, read-only) and adds token validity, system field restrictions, and diff behavior beyond what annotations provide.

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?

Well-structured with intro, prerequisites, workflow, examples, and args/returns. Concise with no wasted words.

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?

Complete coverage: explains return schema, examples cover common cases, and distinguishes from siblings. No gaps given output schema exists.

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

Parameters5/5

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

Despite 0% schema coverage, description fully explains each parameter: sys_id, table, fields with examples and restrictions on system fields.

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

Purpose5/5

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

Description clearly states the tool previews changes to an existing CI before applying them, without making changes. It uses specific verbs and distinguishes from sibling confirm_ci_update.

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

Usage Guidelines5/5

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

Explicitly states prerequisites (use search_cis or get_ci_details), typical workflow, token expiration, and provides multiple examples showing when to use.

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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