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

Annotations declare readOnlyHint=true and destructiveHint=false, which matches rendering a card, so there is no contradiction. The description adds real behavioral value beyond the annotations: no payment details are collected in chat, the payment happens off-chat at a specific URL, and the recommended next tool is named.

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, zero filler, and the key constraint (no payment in chat) is front-loaded right after the purpose. Every sentence carries distinct information: purpose, constraint, follow-up.

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 an output schema present, return values need not be explained, and the description still covers everything an agent needs: what it renders, what is displayed, where payment occurs, and which tool to call afterwards.

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?

The tool takes zero parameters, so there is no parameter syntax for the description to carry; baseline for a parameterless tool is 4. Schema description coverage is 100% and nothing further is needed.

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 ('Opens the Add credits card with the current wallet balance') and immediately scopes it against the alternative flow: payments never happen in chat, the user taps through to a URL. An agent can tell this apart from the other credit/billing 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?

Clear context for invocation (user wants credits, card is rendered in chat) and an explicit follow-up ('After they add credits there, call ucode_credits_status'). It stops short of naming when NOT to use it versus a direct-purchase sibling such as ucode_agent_buy_credits, so it is context without exclusions.

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