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

Annotations only say readOnlyHint=false and destructiveHint=true; the description goes well beyond by disclosing the entitlement gate, the `wouldDelete`/`confirmDestructive:true` retry contract, the `ONE_WAY_SOURCE_SET_INVALID` mutual-exclusion error, and the 'omitting both preserves sources' default. These are exactly the behavioral traits annotations cannot convey.

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?

Front-loaded with the tool's scope, and the parenthetical asides (back-compat note, error codes, 'N sources fanning into M targets') each add real signal. The opening sentence is dense with clauses and the block runs long, keeping it below a 5.

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 10-parameter, deeply nested mutation with no output schema, the description covers the risky and confusing parts an agent would otherwise get wrong. It is only incomplete on the unexplained `impactToken` and the unenumerated `settings.*` propagation fields.

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?

With 0% schema description coverage the description must carry the load, and it does for the hard parameters: `enabled` maps to pause/resume, `calendars` is an end-state field, `direction`, `confirmDestructive`, and the array-vs-singular `oneWaySourceCalendarIds`/`oneWaySourceCalendarId` distinction with their rejection rule. It leaves `impactToken` and most `settings.*` fields unexplained, so it compensates well but not fully.

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 (update) and resource (sync) and then enumerates the exact editable surface: rename, pause/resume via `enabled`, propagation settings, `direction`, and the `calendars` end-state field. An agent can tell this apart from pause_sync/resume_sync/delete_sync 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 clear operational context: the dashboard-editor mental model, the entitlement prerequisite for `settings.directionalSettings`, and the two-call confirmation flow for destructive calendar removal. It stops short of explicitly naming alternatives (preview_sync_edit, pause_sync) or stating when not to use it, so it lands at 4 rather than 5.

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