Sandbox Topup

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

Annotations declare non-destructive but mutating, non-idempotent behavior; the description goes well beyond that by disclosing the auth requirement (sandbox key), the amount cap (1,000,000) and default, the returned value (new balance), and that the endpoint is unavailable with a live key.

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-loads the critical constraint ('SANDBOX ONLY') and packs purpose, prerequisite, parameter defaults, cap, and return value into three tight sentences with no filler.

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 no output schema, the description compensates by stating it returns the new balance. Auth requirements, scope, caps, and defaults are all covered, so an agent has everything needed to call it correctly.

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 default, cap, unit, and exclusiveMinimum are already documented. The description restates those facts but omits the deprecated `amount` alias that the schema flags, so it adds no meaning beyond the schema. Baseline 3 applies.

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 (grant fake account credit) and resource (sandbox account), and scopes it explicitly with 'SANDBOX ONLY'. This clearly distinguishes it from live-money siblings like top_up_account_credit and configure_auto_topup.

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 the exact triggering condition (after funds run out, so paid register/renew/transfer operations can keep being exercised) and the prerequisite (sandbox API key pk1_sb_). It also states the negative condition: with a live key the endpoint is not available.

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