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

Annotations already declare this is a non-read-only, non-destructive, non-idempotent write, so safety is covered. The description adds behavior annotations cannot carry: the limit is actually enforced by `buy`, and passing null removes the limit rather than setting it to zero — an important semantic distinction.

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 compact clauses, front-loaded with the role and the action, followed by the enforcement consequence and the removal case. No 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?

For a two-parameter write tool with a fully described schema and no output schema, the description covers role, effect, enforcement, and the null case. It stops short of saying what the tool returns or whether the limit is per-currency, which would matter if a user holds multiple currencies.

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 both parameters are already documented, including the null-removes-limit semantics. The description restates the null behavior but adds nothing about currency selection or the default of chf, so it only matches the schema baseline.

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 ('set a monthly spending limit') and scopes it to the 'Buyer' role, which separates it from the seller-side siblings. It also links the effect to the `buy` tool, making its function concrete rather than abstract.

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 'Buyer:' prefix implies this is for buyers, and the reference to `buy` refusing overspend explains the consequence of the setting. However, there is no explicit statement of when to call it versus alternatives, nor any prerequisite such as needing an existing account or mandate.

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