Prepare an eSIM plan for purchase

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

Even with annotations present, the description adds substantial behavioral context: it creates no order, moves no money, reserves nothing, replaces the earlier quote if called again, re-reads price/availability/balance from the platform, and must never imply the plan is reserved or bought. No contradiction with the annotations exists; the openWorldHint aligns with the re-reading behavior.

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?

Though long, the description is tightly structured with clear sections: WHAT, WHEN, FIRST, AFTER SUCCESS, and boundary statements. Every paragraph covers a distinct operational concern, and the opening sentence front-loads the core purpose. No filler sentences are present.

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?

Given the tool's complexity, 6 parameters, output schema, and a web of related sibling tools, the description fully covers prerequisites, side effects, follow-up actions, and post-success messaging. It leaves no meaningful gap for an agent deciding when and how to invoke this tool.

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 schema already documents all six parameters with 100% coverage, so the baseline is 3. The description adds genuine value by insisting bundle_code must come verbatim from a catalogue result and never be invented or asked from the user, plus clarifying that region/country preserve context but never affect price. This goes beyond the schema's already-rich parameter docs.

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?

The description opens with a precise verb+resource statement: prepare a signed-in user's chosen plan for buying and report its cost, while explicitly clarifying that it does NOT buy anything. It clearly distinguishes this from confirm_purchase and create_card_checkout by stating those are the actual paying steps.

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?

The description gives explicit when-to-use context ('a signed-in user has picked a real plan... and wants to go ahead'), prerequisites (must check get_login_status), and directly names the alternatives: confirm_purchase for Wallet and create_card_checkout for Card. It also tells the agent not to call this again for the same choice and not to start payment on its own.

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