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

Annotations already declare destructiveHint=true, idempotentHint=false, and readOnlyHint=false, so the safety profile is partly carried by structured data. The description adds nothing beyond that: no statement of required permissions, whether the change is reversible, what happens to existing mode bits, or what occurs on failure for a destructive mutation.

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

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

A single short sentence with the key concept front-loaded and no wasted words. It is terse to the point of under-specification, but the structure itself is clean.

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

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

For a destructive, four-required-parameter mutation with no output schema and zero schema description coverage, the description is far too thin. An agent cannot learn from it how to scope root, what id refers to, or what the side effects of a mode change are.

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

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

Schema description coverage is 0% across four required parameters. The description only illustrates the mode format ('0755'), which the schema already constrains with pattern ^[0-7]{3,4}$; id, file, and root are entirely undocumented, including what root scoping means for path resolution.

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

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

States a specific verb and resource: 'Change a file mode', with an octal example. An agent can tell this apart from files_edit, files_rename, or files_write without opening the schema, though the description never explicitly contrasts with those siblings.

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

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

There is no when-to-use guidance, no mention of prerequisites, and no routing to alternatives such as files_edit for content changes. The agent must infer from the name alone that this is for permission bits rather than file contents.

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