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

With no annotations, the description must carry the safety profile, and it does disclose two behavioral facts: the grant is one-time and the credits are restricted to the sandbox merchant. It omits what happens on a repeat call (error vs. no-op), whether auth/registration is required, and whether the operation is reversible.

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?

Two short sentences, the grant quantity and one-time constraint front-loaded, followed by the spending restriction. No filler or redundancy.

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 zero-parameter mutation tool with no output schema, the key facts an agent needs are present: what it grants, that it is one-shot, and where the credits are usable. The main residual gap is the missing prerequisite and post-call state, which is minor at this complexity.

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 and the schema is closed (additionalProperties: false), so there is nothing for the description to disambiguate. The baseline for a no-parameter tool 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 and resource ('Grant 10 test credits') plus two qualifiers: one-time ('once') and spending scope ('sandbox merchant'). This separates it in spirit from issue_voucher and get_balance, though it never names an alternative explicitly.

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 word 'once' implicitly tells the agent not to call this repeatedly, which is useful guidance. However, there is no explicit when-to-use context, no prerequisite (e.g. whether register_agent must run first), and no named alternative for non-sandbox credits.

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