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

With no annotations at all, the description carries the full burden, and it does disclose genuinely non-obvious data-quality behavior: spend may be missing before observed_since, and balance may cover the account, a single key, or be unknown. It omits freshness/latency expectations and whether connections must exist first, keeping it from a 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 sentences, front-loaded with the metric list, and every clause carries information. The second sentence is dense with nested parentheticals and quoted enum-like values, which hurts scanability slightly, 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?

With no output schema and no annotations, the description must explain return values and largely does, decoding the two most important fields. Gaps remain: no mention of what happens with zero connected providers, data freshness, or call cost for a cross-provider aggregation.

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?

There are zero input parameters, so the baseline is 4. The description's explanation of spend_basis and balance_scope concerns response fields, not inputs, so it adds no input-side meaning but also has nothing to get wrong.

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?

The description names the resource precisely ('cross-provider rollup') and enumerates the metrics returned: balance, burn rate, days-to-zero, month-to-date spend, projection, rate-limit headroom. 'Cross-provider' implicitly distinguishes it from get_provider and get_request_costs, though no sibling is named 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?

Use is only implied by 'cross-provider rollup' — an agent can infer this is the aggregated view versus per-provider tools like get_provider. There is no explicit when-to-use/when-not statement or reference to alternatives, so the agent must infer the selection rule.

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