credits_balance

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

With no annotations supplied, the description carries the full disclosure burden. It does add one genuinely useful behavioral fact — that authentication is required — but says nothing about read-only safety, error behavior when logged out, or freshness of the balance.

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 the resource and followed by the auth requirement; nothing is padded. It is arguably too terse rather than verbose, but every sentence earns its place.

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 tool that has an output schema, the description covers what is returned and the auth requirement, which is close to sufficient. However, the account-vs-Cumulus scope ambiguity is left unresolved, which matters given how many overlapping wallet and points siblings exist.

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 schema declares zero properties at 100% coverage, so there is nothing for the description to clarify. Baseline 4 applies for a parameterless tool; the description at least confirms it is account-scoped with no inputs.

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?

Names a specific resource — the Migros account credit balance — so the agent knows it returns a monetary/credit figure rather than points or bons. It does not explicitly distinguish itself from near-neighbours like cumulus_points, cumulus_wallet, or cumulus_bons, which is the only thing keeping it from a 5.

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?

'Requires login' is a precondition, but there is no guidance on when to choose this tool over the many other balance/wallet-style siblings. No exclusions, no alternatives, no statement about what happens if the agent is unauthenticated.

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