Google Compute Engine

list_instance_group_managers

Read-onlyIdempotent

Lists Compute Engine managed instance groups (MIGs). Details for each MIG include name, ID, instance template, base instance name, target size, target stopped size, target suspended size, status and creation timestamp. Requires project and zone as input.

Input Schema

TableJSON Schema

Name	Required	Description
`zone`	Yes	Required. The zone of the instance group managers.
`project`	Yes	Required. Project ID for this request.
`pageSize`	No	Optional. The maximum number of instance group managers to return.
`pageToken`	No	Optional. A page token received from a previous call to list instance group managers.

Output Schema

TableJSON Schema

Name	Required	Description	Default
`nextPageToken`	No	A token that can be sent as `page_token` to retrieve the next page. If this field is omitted, there are no subsequent pages.
`instanceGroupManagers`	No	The list of instance group managers.

TDQS

A3.6/5.0

Behavior3/5

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

Annotations already disclose readOnlyHint, idempotentHint, and destructiveHint, covering the safety profile. The description adds the return fields and required inputs, but does not disclose additional behavioral aspects like pagination limits or error cases. No contradiction with annotations exists.

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?

The description is composed of two tight sentences, front-loaded with the main action, and contains no redundant information. Every sentence contributes to understanding the tool's function and inputs.

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

Completeness4/5

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

Given the presence of an output schema and strong annotations, the description provides adequate context for a straightforward list operation. It identifies the resource, return fields, and required inputs, though it omits discussion of pagination or cross-zone limitations. These are minor gaps for a simple tool.

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

Parameters3/5

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

Schema description coverage is 100% for all four parameters, so the description does not need to elaborate on them. The description only repeats that project and zone are required, adding no further semantic nuance beyond the schema.

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?

The description clearly states the tool lists Compute Engine managed instance groups (MIGs) and enumerates the details returned, such as name, ID, and status. It is specific about the resource and action, but does not explicitly differentiate from sibling tools like list_managed_instances, which lists instances within a group.

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?

The description implies its usage for listing MIGs and mentions required project and zone inputs. However, it offers no guidance on when to prefer this tool over alternatives, such as list_managed_instances for individual instances, nor does it specify limitations like zone-scoped listings.

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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TDQS

A3.6/5.0

Disambiguation5/5

Each tool targets a distinct resource-action combination. For resources with both basic and detailed getters (reservations, templates), the suffixes clearly differentiate them, and list vs get distinctions are unambiguous. No two tools appear to do the same thing.

Naming Consistency5/5

All tool names follow a consistent verb_noun pattern with snake_case (e.g., create_instance, list_disks, get_zone_operation). Getters consistently use descriptive suffixes like basic_info, details, or properties. No mixed naming conventions or vague verbs.

Tool Count4/5

29 tools is slightly above the ideal range but justified given the breadth of Google Compute Engine resources covered (instances, disks, templates, reservations, commitments, MIGs, snapshots, images, machine types, accelerator types). Each tool serves a specific purpose and contributes to the overall scope.

Completeness2/5

The toolset is heavily read-oriented. While instances have full lifecycle coverage (create, delete, start, stop, reset, set machine type), most other resources lack write operations: disks, templates, reservations, commitments, snapshots, and MIGs only have get/list tools. This creates dead ends for agents needing to create or modify these resources, which is a significant gap for a GCE management server.

Resources

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