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

Annotations already declare readOnlyHint=false and idempotentHint=false, so the non-idempotency restatement adds little. The genuinely additive content is the side-effect boundary ('does not assign a membership or send an invoice') and the 'real member record' framing, which tells the agent the write is persistent and what it does not trigger.

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 WRITE marker, then requirements, side-effect boundaries, the idempotency warning and the endpoint. Every clause carries distinct information and none is padding.

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 create tool with no output schema, the description covers safety, side effects and duplicate risk well. It does not say what comes back from POST /member (e.g., the new member's identifier), which an agent chaining a follow-up get_member call would want, but that is a minor gap given annotations cover the safety profile.

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% and all six parameters are documented with types, lengths and an enum, so the schema carries the load. The description only restates which fields are required versus optional, adding no format or constraint detail beyond the schema.

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 ('WRITE: create a new member in the club') and immediately bounds the scope by saying it does not assign a membership or send an invoice. This lets an agent separate it from hello_club_create_transaction and membership-related siblings without opening a 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 directs the agent to call hello_club_list_members first to avoid duplicates, which is a concrete when-to-use instruction tied to the non-idempotent behavior. It stops short of naming when NOT to use it (e.g., for bulk import or for existing members), so it is strong but not exhaustive.

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