set_default_payment_method

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

Beyond the destructiveHint/openWorldHint annotations, it discloses what actually changes (an account-wide default that persists across the app/web and every future order), that the call is interactive ('Prompts the user at the terminal'), a version prerequisite (dd-cli >= 0.2.6), and a required follow-up ('Re-preview any existing cart afterwards'). These are exactly the non-obvious operational facts an agent needs before invoking a destructive, blocking mutation.

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?

The account-wide scope leads, followed immediately by the use-condition, the alternative, and then operational caveats. Five short sentences, each carrying a distinct fact, with no restatement of the tool name or schema content.

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 destructive, interactive mutation with an adequately documented schema and no output schema, the description covers consequences, the interactive prompt (so the agent knows it blocks on user input), version requirements, and the post-call re-preview obligation. Nothing an agent needs to call it safely is missing.

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 card_id, display_name, and intent are already documented in-schema, which sets the baseline at 3. The description adds no parameter-level detail of its own — notably it does not say that display_name drives the confirmation prompt or that card_id must come from list_payment_methods, both of which remain only in 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 (change the default card) plus its scope (account-wide, persisting to app/web and all future orders). It explicitly distinguishes itself from the single-order payment path via preview_order/submit_order, so an agent can route correctly without opening sibling schemas.

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 gate ('Use ONLY when the user asks to change their default') and names the alternative route with the exact parameter to use instead ('pass card_id to preview_order and submit_order'). This is the when/when-not/alternative triad in compressed form.

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