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

Beyond the annotations, the description discloses that no overwrite occurs, that the extension may change as a side effect, and that files:write plus account permissions are required — none of which is in the structured fields. It also warns about uncertain results and recommends inspection before retrying, which usefully tempers the destructiveHint=true and idempotentHint=true combination without contradicting them.

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?

Four short sentences with no filler, and the core action plus the no-overwrite constraint are front-loaded. The closing retry sentence is slightly cryptic in isolation but still earns its place as operational guidance.

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?

An output schema exists, so return values need not be explained, and annotations cover the safety profile; the description adds permissions, overwrite, and extension behavior on top. The remaining gap is parameter meaning for a two-parameter tool with zero schema documentation, which an agent would need in order to call it confidently.

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%, so both parameters (file_hash and file_name) are undocumented in the schema, and the description never explains what file_hash identifies or that file_name carries the extension. The only indirect clue is 'may change its extension,' which hints that file_name includes one, leaving most parameter meaning to inference.

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?

The description states a specific verb and resource ('Rename an editable, unlocked file') plus the scope constraint that it may change the extension, which separates it from the folder-renaming sibling. It does not explicitly name filesfm_rename_folder or filesfm_move_file as alternatives, so differentiation is implied by the resource noun rather than stated.

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?

Preconditions for use are given ('editable, unlocked'), and there is one piece of situational guidance about inspecting the destination before retrying an uncertain result. However, there is no explicit when-not guidance and no alternatives named, so an agent must infer that locked/non-editable files or overwrite scenarios are out of scope.

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