Buy a residential proxy package

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

Annotations already flag destructiveHint=true, non-idempotent and open-world, but the description adds real value beyond them: the account balance is charged immediately, and estimate_only=true is a no-charge preview path. The free later geo change is useful operational context. It does not describe whether a repeat call buys a second bundle or what is returned, so not a 5.

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 what is being purchased, then the charging behavior, then the optional-parameter escape hatch - no filler sentences. Slightly dense, packing the geo workaround into the same breath as the country parameter, but every clause 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?

For a non-idempotent purchase tool with no output schema, the description covers the critical facts an agent needs: immediate charge, the estimate-only escape hatch, and country optionality with a free post-hoc alternative. It omits what a successful purchase returns (package id, traffic amount) and whether buying twice stacks, which keeps it from a 5.

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 the baseline is 3. The description echoes the schema's semantics for estimate_only and country (optional, global pool default) but adds nothing about the num multiplier or price_id linkage beyond what the schema already spells out.

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+resource (buys a residential proxy) and immediately disambiguates it from the time-rental sibling tools by calling out that it is 'a traffic bundle rather than a time rental.' An agent can separate this from buy_proxy/renew_proxies/add_residential_traffic without opening any 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 clear context: use estimate_only=true to price without charging, and country can be omitted for a global pool because set_residential_geo can change geo later for free - effectively naming an alternative for post-purchase adjustment. It never states explicitly when to pick this over buy_proxy or add_residential_traffic, so it falls short of full when/when-not guidance.

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