Get Account Balance

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

Annotations already declare readOnlyHint=true, so the safety profile is covered; the description adds genuine value by disclosing the exact response keys and the null edge cases (all three None when no balance block, available alone None when unreported). It does not mention auth requirements or rate limits, but for a read-only balance lookup that is a minor gap.

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-loaded with the purpose and the sibling comparison in the first sentence, then a compact return-shape paragraph. Slight redundancy with the existing output schema, but nothing is wasted.

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 one-parameter read tool with an output schema and readOnlyHint, the definition covers selection rationale and the non-obvious null semantics. Only authentication context is absent, which is not critical here.

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 100% and the single account_id parameter is already documented as an Akahu account id. The description adds no format, sourcing, or validity guidance beyond the schema, so the 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 and resource ('Return just the balance for an account') and immediately contrasts scope with the sibling acct_get_account. An agent can distinguish this from acct_get_account 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?

'Cheaper than get_account' gives a concrete cost-based selection signal for choosing this over the richer sibling. It stops short of explicit when-not guidance (e.g. use get_account when you also need account metadata), but the routing intent is clear.

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