openstack-mcp-server

List host aggregates

list_aggregates

Read-onlyIdempotent

Lists Nova host aggregates with availability zones and hosts to inspect compute placement; use filters and ensure sufficient role, since forbidden indicates missing permissions, not an empty result.

Instructions

List Nova host aggregates with availability zone and hosts. Usually needs more than a project reader role; forbidden means the role is missing, not that the list is empty. Not paged; narrow with filters.

Input Schema

Name	Required	Description	Default
`limit`	No	Maximum items to return (1-100, default 50).
`project_id`	No	Project ID to work in; omit for the default project. Allowed values are listed by get_scope.

Output Schema

Name	Required	Description
`items`	Yes
`limit`	Yes	Maximum number of items requested.
`complete`	Yes	True when no more items exist beyond this page.
`resource`	Yes	Resource type of the items.
`project_id`	Yes	Project whose session produced the list.
`next_marker`	No	Pass as marker to read the next page; null when complete or when the API has no marker paging.
`observed_at`	Yes	UTC time the list was read.

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Oct 30, 2026

TDQS

A3.7/5.0

Behavior4/5

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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), and the description goes beyond them by disclosing the auth-role requirement and decoding the forbidden response ('forbidden means the role is missing, not that the list is empty') — a genuinely useful behavioral cue. The 'Not paged' claim is slightly at odds with a limit parameter, but the added operational context still outweighs that.

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

Conciseness4/5

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

Three short, front-loaded sentences with no filler; the resource and return fields come first, followed by caveats. The trailing 'Not paged; narrow with filters' is slightly compressed to the point of ambiguity given the presence of a limit parameter.

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?

For a two-parameter read-only list tool with a full output schema, the description covers the important gaps: permission requirements, what a 403 means, and pagination expectations. Nothing essential for a correct call is missing.

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 coverage is 100%, so both the limit and project_id parameters are already fully described in the schema, establishing the baseline of 3. The description's 'narrow with filters' adds nothing, and neither parameter is actually a filter, so it does not enrich parameter meaning.

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 ('List Nova host aggregates') and adds the returned content ('with availability zone and hosts'), which lets an agent know what to expect. There is no near-identical sibling to distinguish from, so no explicit differentiation is needed.

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 gives a prerequisite ('Usually needs more than a project reader role') and tells the agent to 'narrow with filters', which implies usage context. However, it never states when to choose this tool over another or what a typical call scenario looks like, leaving guidance largely implicit.

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