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

Annotations already declare destructiveHint=true, openWorldHint=true, and idempotentHint=true, so the safety profile is partly carried structurally. The description adds the analytical contract (separate realized savings from avoidance, surface assumptions) but never explains why the call is flagged destructive, that it transmits sources to an external inference provider, or that it may consume a paid invoice — all of which the agent must dig out of 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?

A single front-loaded sentence with three purposeful clauses and no filler; the deliverable leads and the qualifiers follow. It is efficient, though the three clauses compress a fairly complex contract into one line without structural cues.

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?

This is a complex nested-payload tool with a required external-processing consent flag, an idempotency key, an optional invoice, and no output schema. The description covers the analytical intent but omits the external-processing/privacy posture and gives no sense of what comes back (a TCO model? a narrative?), leaving meaningful gaps for a first-time caller.

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 67% with the nested `inputs` object documented field-by-field (context, years, currency, documents, cost baselines), so the schema does most of the work. The description adds no parameter-level meaning of its own — notably silent on `sourceFields`/`sourceRunIds` chaining and on the consent flag — but the baseline for this coverage level is met.

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 states a specific verb and deliverable — build a TCO and savings case — plus the analytic stance (realized vs. avoided savings, surfaced assumptions). An agent can tell this is a finance/TCO deliverable rather than a data lookup. It stops short of distinguishing itself from the closest sibling, xsavings-narrative, which also produces savings content.

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?

The phrase 'for finance review' implies the context in which to reach for this tool, but there is no explicit when-to-use or when-not-to-use guidance and no alternative named (xsavings-narrative, xvendorbench, or the category tools are all plausible neighbors). The agent must infer selection from the title alone.

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