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

Annotations already declare the mutation profile (readOnlyHint=false, destructiveHint=false, idempotentHint=true), so the description's added value is the token lifecycle: single-use and a 15-minute expiry, which tells the agent a repeat call will not work. It does not describe what happens after expiry or what is returned, but the critical behavioral facts are present and consistent with a non-destructive reverting operation.

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?

Two sentences, both load-bearing: the first defines scope, the second encodes the token constraints and the sibling routing. Nothing is repeated from the title and the exclusion is placed where an agent will read it.

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 single-parameter mutation with no output schema and rich annotations, the description covers scope, input provenance, lifetime limits and the sibling alternative. Only the failure mode for an expired or already-used token is left implicit.

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 the token parameter is already documented; the description goes beyond that by explaining the token's provenance (returned by the change being undone) and its one-use/15-minute lifetime. That is genuinely useful semantics the schema does not carry.

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 ('Reverses one change to a folder's contents') and then enumerates exactly which change types are covered (added, removed, moved, copied, kept matches, marked seen). This distinguishes it from siblings like restore_folder or delete_folder without the agent needing to open any schema.

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?

Gives the selection condition for the input (use the undo_token returned by a folder change), an explicit exclusion with a named alternative ('A deleted folder comes back with restore_folder instead'), and a hard constraint on when it can be used (one use, 15 minutes). An agent can choose between this and restore_folder without inference.

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