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

Annotations already declare idempotentHint=true and destructiveHint=false, but the description adds the concrete behavior behind that hint: 'Asking for a folder that already exists succeeds and returns it.' That is genuinely useful context an agent cannot infer from the hint alone. It does not discuss permissions or error cases, so not a 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, each carrying distinct information (purpose, idempotency semantics, optional parent usage), with the core action stated first. No filler or restatement of the name.

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?

Covers purpose, idempotency, and the one non-obvious parameter; an output schema exists so return values need not be explained. Missing only explicit guidance on discovering account_id or handling failure cases, which are minor given the schema descriptions and annotations.

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 baseline is 3, but the description adds real meaning beyond the schema by clarifying that 'parent' accepts a path or a name and should be sourced from list_folders. That resolves the ambiguity of whether the value is an ID, path, or display name.

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 ('Create a folder in a mailbox') with the scoping detail that the folder lives in a mailbox, and the subfolder case is called out. It does not explicitly name sibling tools, but the resource is distinct enough from create_draft, move_message, and list_folders that an agent can route without opening the 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 a concrete condition for the optional parameter ('Give "parent" ... to create a subfolder') and points at list_folders as the source of valid parent values. It stops short of stating when not to use this tool (e.g. if a folder already exists, prefer list_folders) or other preconditions, so it falls just short of full routing guidance.

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