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disks/mounts

Read-onlyIdempotent

Lists mounted filesystems with device, mount point, type, and options, optionally filtered by filesystem type. Use privileged mode in containers to see host mounts.

Instructions

Lists mounted filesystems (device, mount point, type, options) from /proc/thread-self/mounts, sorted by mount point. Read-only. fs_type filters by exact type (ext4, overlay, tmpfs; no globs). It reads the daemon's own mount namespace, so in a container use privileged: true (needs a grant) to get the host's mounts. Text lines look like /dev/sda1 on /mnt type ext4 (rw,...); output_format: json returns an array of objects (device, mount_point, fs_type, options), or null rather than [] when nothing matches (text is then empty). For block devices use disks/list, for the space used on a mount disks/free.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
fs_typeNoExact filesystem type, no globs (e.g. 'ext4', 'overlay', 'tmpfs')
privilegedNoRun as root. Needs a grant for this tool in mcp-sudo.yaml, otherwise refused
output_formatNoUse json for structured output (yaml, table and wide return the same JSON); default is text

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed3 schema fields changedv0.4.1
    • changedInput schema / properties / fs_type / description
      Previous value: -"Only include mounts of this filesystem type (e.g. 'ext4', 'overlay', 'tmpfs')"New value: +"Exact filesystem type, no globs (e.g. 'ext4', 'overlay', 'tmpfs')"
    • changedInput schema / properties / output_format / description
      Previous value: -"Desired output format (e.g. json, yaml, table, wide). Defaults to text"New value: +"Use json for structured output (yaml, table and wide return the same JSON); default is text"
    • changedInput schema / properties / privileged / description
      Previous value: -"Run as root"New value: +"Run as root. Needs a grant for this tool in mcp-sudo.yaml, otherwise refused"
  2. First observed

TDQS

A4.8/5.0
Behavior5/5

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

Annotations already declare readOnly/idempotent/non-destructive, so the bar is lower; the description still adds real context: it reads the daemon's own mount namespace, container usage requires a privileged grant, and it documents an edge case (returns null rather than [] when nothing matches). This is behavioral information not present in annotations or schema.

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?

Front-loaded with the core purpose and data source, then constraints, then output shape, then sibling routing. It is a dense single block but nearly every clause carries actionable information; only the textual line-format example is arguably illustrative filler.

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?

No output schema exists, but the description compensates by describing both the text line format and the JSON array shape (device, mount_point, fs_type, options) plus the null-when-empty behavior. Combined with the routing and privilege notes, nothing needed to call it correctly is missing.

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 3 is the baseline, but the description adds meaning beyond it: fs_type is an exact match with no globs, privileged needs a sudo grant or is refused, and json vs text output behavior (with the null edge case). It enriches the parameters rather than merely restating them.

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?

Specific verb+resource: 'Lists mounted filesystems (device, mount point, type, options)' with an explicit data source (/proc/thread-self/mounts) and ordering. It also names the neighboring tools it is not ('For block devices use disks/list, for the space used on a mount disks/free'), so an agent can disambiguate without opening a schema.

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 routes to alternatives: disks/list for block devices and disks/free for mount usage. It also states the precondition for host mounts in a container (privileged: true, which needs a grant), covering when-to-use and a key constraint rather than leaving it to inference.

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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