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

Beyond the annotations (destructiveHint=true, idempotentHint=true), the description supplies the crucial behavioral fact that editors/readers lists REPLACE the current ones, plus authorization requirements, Pro-tier gating, encryption restrictions, and the 50-person limit. That is exactly the context an agent needs before invoking a destructive, idempotent 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?

Dense and front-loaded, leading with the operation and then enumerating access modes in order of restrictiveness. The quoted-key shorthand ("access "public": ...") is terse to the point of being slightly cryptic, but no sentence is wasted.

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 authorization, tier limits, encryption constraints, and the replacement semantics that a mutation tool most needs, and no output schema exists so return values needn't be described. The one real gap is the conditional requirement of editors/readers for the "emails" mode, and no mention of what failure looks like.

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; the description earns above baseline by explaining what each access value actually means ("public" = anyone with the link, "emails" = owner plus listed readers, editors can also edit) and that the lists overwrite existing entries. It does not say whether readers/editors are required when access="emails".

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 ("changes who can open the user's note or whiteboard") and scopes it to the owner's own items. It does not, however, differentiate itself from the sibling set_read_only, which an agent could plausibly confuse with this permission-modeling tool.

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 clear preconditions: only the owner can change access, "only_me"/"emails" are Pro features, encrypted items can't be shared by email, and lists cap at 50 people. It never explicitly says when to prefer this over set_read_only, so the routing guidance is implicit rather than complete.

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