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

No annotations are provided, so the description carries the burden. It discloses two real behavioral facts beyond the schema: 'Owner_key required' (a permission/credential constraint) and 'An unknown group_by is an error' (failure mode). It does not state what the totals are scoped to by default beyond the schema default, but for a read-only aggregation tool this is solid disclosure.

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 sentences, each earning its place: output shape first, then the use case plus follow-on tool, then the two constraints. Front-loaded with the value proposition and free of filler.

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?

An output schema exists, so return values need not be detailed, yet the description still names the key fields. Combined with 100% schema coverage and the explicit credential/error notes, an agent has everything needed to call this correctly relative to its sibling tools.

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%, so the baseline is 3. The description adds meaning on top: it emphasizes that an owner key is required for api_key, and that an unrecognized group_by value errors rather than falling back to a default — both facts the schema does not state explicitly.

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+resource+output shape: it aggregates spend totals from the audit log, returning per-group total_cost (units) and calls. It also distinguishes itself from the raw-log sibling by saying it works 'instead of reading every entry', so an agent can route between this and aanet_get_activity 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 explicit context and the follow-on action: 'Use it to see which sub-agent is burning budget before adjusting a budget_cap via aanet_update_subkey.' It also states the when-not condition (don't read every entry) and the alternative tool by name.

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