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

The annotations already declare destructiveHint=true and idempotentHint=true, and the description adds real context beyond them: the no-op outcome ('Returns `closed=false` if no live conversation was open') and the postcondition that the next `design_chat` starts fresh. What it does not spell out is what state is lost when the conversation closes — whether transcript or design context is discarded — which is the main unknown for a destructive operation.

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 action, then the return case, then the postcondition, then usage — a logical order with no filler sentences. It is slightly mixed in register, interleaving interface contract (return value) with conversational policy (payment guidance), but every sentence carries information.

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?

With two required parameters, an output schema already documenting `closed`, and destructive/idempotent annotations, the description covers the trigger condition, the no-op path, and the postcondition. The remaining gap is parameter provenance — an agent still does not know how to obtain or validate `session_id` and `design_id`.

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 0%, so the description carries the full burden for both required parameters. It merely names `design_id` ('this session and `design_id`') and never defines `session_id`, where either value comes from, or whether `session_id` is the transport session or a design-scoped identifier. Naming a parameter is not adding semantics.

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 — 'Close the held Artifex conversation' — scoped by session and `design_id`, and explicitly frames what comes next ('a fresh `design_chat` starts a new conversation'), which separates it from the sibling that opens one. An agent can distinguish this from `design_chat` 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?

Gives an explicit trigger ('when the customer finishes the design or asks to pay') and an explicit disambiguation rule against a sibling behavior: 'A finished design is not a request to pay: create the payment link only when the customer asks to pay.' That is a concrete when-to-use plus a guardrail against premature `order_create_payment_link`.

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