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

Annotations already declare readOnlyHint=false and destructiveHint=false, and the description adds real value on top: the authorization requirement ('Needs an owner, admin or finance member') and the round-trip instruction to send the policy 'in the shape it comes back.' These are non-obvious operational details an agent would otherwise miss.

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?

It is compact and leads with the action keyword, but it is a single run-on sentence packed with nested parentheses that takes effort to parse. The information is useful but the structure hurts readability.

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 mutation tool with an output schema and annotations covering safety, the description supplies the key missing pieces: permission requirements, the three action modes, and the period format. Return-value explanation is unnecessary given the output schema. Minor gap: no note on non-idempotency or side effects of reopening a period.

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 carries the full burden. It does explain the action enum values, the period format (YYYY-MM), and the intent of the policy object ('send policy, in the shape it comes back'), but the policy payload shape remains opaque and nothing explains what happens when period is omitted or which action requires which optional param.

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 three concrete action values (policy, reopen, true_up) and what each does at a high level, so an agent can tell this is a month-end mutation dispatcher. The phrasing is dense and parenthetical ('action policy (how costs are booked; send policy, in the shape it comes back...)'), which slightly obscures the top-level purpose, but the verb+resource is inferable.

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?

It gives implicit routing: 'policy' for booking costs, 'reopen or true_up' for posting a correction to the invoice. However, it never distinguishes reopen from true_up, nor does it point away from close siblings like month_end, approve_month, or reconciliation_status. Usage is implied rather than stated with alternatives or exclusions.

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