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

Annotations already declare readOnly, idempotent, non-destructive, closed-world, so the safety profile is covered. The description adds genuinely new behavioral context: the call is a fan-out composite that saves round-trips, and the VAT section is conditionally included ('if registered'), which an agent could not infer from the schema.

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?

The payload enumeration is front-loaded where it matters, and the use-case sentence follows immediately. The closing sentence about round-trip savings is mild justification padding but does carry differentiation value, so nothing is seriously wasteful.

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, the description does the heavy lifting by enumerating returned sections, and the conditional VAT section clarifies return shape variance. It does not mention pagination or size/volume characteristics of the composite response, which is the main remaining gap for a fan-out read.

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 description coverage is 100% and already documents the company resolution rules and the period_start/period_end defaults (previous calendar month). The description adds nothing about parameter behavior, 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 ('composite read returning everything needed to close a month in one call') and enumerates the exact payload: P&L, balance sheet, VAT summary, unreconciled count, outstanding invoices, deadlines. It also distinguishes itself from the sibling report tools by framing itself as a one-call aggregate.

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 triggering contexts ('month-end', 'how did we do in [month]', period close, one-shot health view) and contrasts with the alternative of calling each report tool separately. It stops short of naming which specific sibling to prefer when the user only wants one report, 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.