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

Goes well beyond the annotations (readOnlyHint=false, idempotentHint=true, destructiveHint=false) by disclosing the asymmetric effect: decreases take effect immediately while increases return an approvalUrl that the signed-in account owner must approve. That is exactly the kind of non-obvious behavioral trait an agent must know before calling, and it also flags the call as free.

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?

Three short sentences with the mutation effect front-loaded, the approval branch second, and the cost note trailing. Every sentence adds information; nothing is restated from the schema 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 single-parameter mutation with no output schema, the description supplies the missing return shape (approvalUrl on raises), the human-approval dependency, and the immediate-apply semantics for decreases. Nothing an agent needs in order to call this correctly is absent.

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 coverage is 0%, so the description must carry the parameter burden; it does by naming the unit (credits) and the cadence (daily) that the schema's bare 'dailyCreditCap' integer does not. It still omits any discussion of the 0–100000 bounds or what a cap of 0 means, so it is good but not exhaustive.

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 ('Set this key's daily agent spending cap in credits'), with the unit and the scope ('this key') made explicit. It is clearly the write counterpart to the sibling autoshort_get_limits, so an agent can distinguish them without opening either 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 concrete operating context: lowering applies immediately, raising requires owner approval, and an agent cannot raise its own cap. It does not explicitly name autoshort_get_limits or autoshort_buy_credits as alternatives, so guidance is strong but not a full when/when-not routing statement.

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