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

With readOnlyHint=false, idempotentHint=true and destructiveHint=false already supplied, the description still earns credit by disclosing three non-obvious traits: the extension is forced from the real content, existing shared links continue to work, and the returned link reflects the new name. It does not cover name-collision behavior or permission requirements, which keeps it below 5.

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?

Three short sentences, front-loaded with the action, then the extension rule, then link-continuity behavior. Every clause carries distinct information and nothing is repeated from the schema or annotations.

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 two-parameter, fully documented, fully annotated tool with no output schema, the description covers the mutation's side effects and even the return value (a new link). Only edge cases such as duplicate-name handling are absent, which is a minor gap at this complexity.

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 coverage is 100%, so file_id and new_name meaning are already documented in the schema and the baseline is 3. The description does add one bit of semantic value by implying the extension portion of new_name is governed by the underlying content, but that is the only supplementation.

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?

"Renames a file" states a specific verb and resource, and the resource noun cleanly separates it from the sibling rename_folder. It stops just short of explicitly naming that alternative, so it is clear rather than maximally distinguishing.

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?

The parenthetical "(every plan)" gives availability context, which is useful, but there is no explicit when-to-use guidance versus siblings such as replace_file or move_file, nor any stated prerequisites. Usage is implied by the tool's obvious purpose rather than described.

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