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

Adds real context beyond the annotations: who is reachable (paid members only), the failure mode for free members, the confirmation default, and the API-key requirement. The outbound/consequential nature is reinforced ('Reaches other people: confirm with the user'), which is the meaningful risk profile for a send action.

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?

Purpose is front-loaded well, but the confirmation guidance is stated twice ('By default you confirm each call; you can switch that off' and 'Reaches other people: confirm with the user before each call'), which is redundant. Several sentences could be merged without loss.

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 2-param mutation tool with no output schema, the description covers eligibility, error behavior, confirmation, and auth. Missing only explicit routing to the alternative tool for tier/free-member cases, but nothing needed to call it correctly is absent.

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 member_id and body are already documented in the schema. The description adds no syntax, format, or constraint detail about the parameters, 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?

Specific verb+resource+scope: 'direct message to one current or former paid member, as you.' The 'one member' scoping distinguishes it from the bulk sibling patreon_message_tier and from list_chats/list_members. An agent can select it 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?

Explicitly states the eligibility constraint ('Patreon allows direct messages only to current or former paid members, so a free member returns an error'), which tells the agent when a call will fail. It stops short of naming the alternative tool (e.g. patreon_message_tier) for bulk/other messaging.

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