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

Annotations already declare readOnly, idempotent, non-destructive, and open-world, and the description corroborates the open-world claim by sourcing other providers' public prices. It adds useful context that output is denominated in BRL and includes per-user licensing and renewal-window commentary. However, it does not disclose the confirmation/flagging behavior tied to confirm_unusual_cost, nor how current or authoritative the external price data is.

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 core computation before the secondary outputs. Nothing is padded, though the trailing 'also notes...' clause is slightly vague about whether those items are returned values or advisory commentary.

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 a read-only profile, the description does the necessary work of sketching what comes back: per-document cost, annual cost, provider comparison, licensing, and renewal timing. The main residual gap is the unusual-cost confirmation loop, which affects how an agent must sequence calls.

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 three parameters carry enums, so the schema already documents meaning thoroughly, including the 'none' provider case and the confirm_unusual_cost gate. The description adds only indirect semantics, such as the fact that volume is used for a like-for-like comparison. Baseline 3 is appropriate when the schema does the heavy lifting.

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: it calculates cost per signed document and per year and compares against public prices of other providers at the same volume in BRL. An agent can tell exactly what it produces. It only misses a 5 because there are no siblings to distinguish from, so the differentiating half of the criterion cannot apply.

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?

Usage is implied by the phrasing (comparing an existing e-signature bill against market prices), but the description never says when to call it, when not to, or what prerequisites exist. Critically, it omits the conditional flow implied by confirm_unusual_cost: the tool may flag an unusually high per-document cost and require user confirmation before re-running. That is an invocation rule left entirely to the schema.

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