Plan to give an event service to a helper outside ChurchTools

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

The description adds real behavioral context beyond the annotations: it writes nothing to the event, it returns a plan, and the resulting assignment gets a new id visible through ct_get_event. The 'writes nothing' phrasing sits in mild tension with readOnlyHint=false, but this is coherent because submitting a plan creates server-side plan state (which ct_execute_plan later applies) while the event itself is untouched.

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, front-loaded with the most important safety fact ('Writes nothing'), then the alternative, then the result behavior. No filler and nothing repeated from the schema.

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 plan-producing mutation tool with no output schema and fully documented params, the description covers purpose, the alternative tool, and where the outcome is observed. The one meaningful gap is not stating that the returned plan is applied through ct_execute_plan, which leaves the plan lifecycle 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 description coverage is 100%, so every parameter (eventId, eventServiceId, name, agreed, comment) is already documented, including the critical 'not the serviceId' clarification on eventServiceId. The description adds no format or constraint detail beyond that, so the 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: it 'returns a plan that fills one service assignment of an event ... with the name of a helper who has no ChurchTools account.' It immediately distinguishes itself from the sibling ct_assign_event_service by naming the condition (external vs. ChurchTools helper), so an agent can pick correctly without opening either 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?

Explicit routing rule: 'For a ChurchTools person use ct_assign_event_service' — a clear when-not with the named alternative. It also tells the agent where the result surfaces (ct_get_event). It omits the fact that the returned plan must be applied via ct_execute_plan, which is the other half of this tool's usage flow.

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