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

Annotations already declare readOnlyHint=false and destructiveHint=false, but the description adds a meaningful guarantee beyond them: earlier deals are unchanged, so the assignment is forward-only from the effective date. It does not cover idempotency or what happens when an agent is already on a plan, but the added non-retroactivity detail is real value.

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 tight sentences with no filler; the prerequisite, scope rules, and non-retroactivity each appear once. The leading parenthetical prerequisite pushes the actual purpose into second position, which is a minor structural weakness.

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 four-parameter mutation with full schema coverage and present annotations, the description supplies the prerequisite, the default date, and the non-retroactive scope. No output schema exists, but the description does not explain what is returned or how partial failures are reported, leaving a small gap.

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 description coverage is 100%, so agents, plan_id, workspace_key, and effective_from are already documented, including the 'all' token and the YYYY-MM-DD default. The description only restates the accepted shapes and adds no format or edge-case detail beyond the schema, so baseline 3 applies.

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: put agents on a plan, with the scope made explicit (one agent, a list, or 'all') and a start date. It is clearly a write/assignment operation and distinguishable from plan-creation siblings, though it never names an alternative 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 a concrete prerequisite (workspace_key from create_workspace) and the default behavior for the start date, which tells the agent how to call it correctly. It does not state when to prefer this over create_plan/update_plan or what to do if the agent list is invalid.

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