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

Annotations already declare readOnly, idempotent, closed-world and non-destructive behavior, so the safety profile is covered. The description adds non-obvious context the annotations cannot: the live-key + balance-scope auth requirement and the test-key restriction. It does not cover rate limits or response shape, hence 4 rather than 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?

Two short sentences, front-loaded with what is returned and followed by the prerequisite. No filler, no repetition of the title or annotations.

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 read with no output schema, the description covers purpose and auth gating. It only lightly gestures at the return values ('available and held credits') without saying whether they are returned as separate fields or a formatted string, which is the one remaining gap.

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?

Zero parameters, so there is nothing for the description to disambiguate; the 100% schema coverage baseline applies. The description correctly adds no fake parameter narrative, keeping it clean.

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 ('Read') and resource ('workspace available and held credits'), and the scope word 'live' distinguishes it from anything test-mode. Among siblings (submit_job, get_job, get_results, verify_email, cancel_job), this is unmistakably the balance-read tool.

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 a concrete usage precondition: a live key with balance scope is required, and test keys cannot read real balances. That tells an agent when this call will fail and why. It stops short of naming alternatives or explicitly excluding other balance endpoints, so not a 5.

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