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

With no annotations, the description carries the full burden and discloses real behavior: precedence ("first matching rule wins"), the default fallback ("anything unmatched needs approval"), the auth requirement, and the preview/confirm flow. The main gap is that it never states whether existing rules are replaced or merged, which matters for a set-type mutation.

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?

Dense and front-loaded, opening with the purpose and then packing the rule structure and workflow into compact notation. Every element earns its place, though the inline object notation sacrifices a little readability for density.

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 0% schema coverage, the description still covers purpose, the rule object structure, precedence, default behavior, auth, and the two-step confirm workflow. Only the replace-vs-merge semantics and return value are unaddressed, which are minor relative to what is provided.

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% and the schema types both params only loosely (rules as opaque array of objects), so the description must compensate. It explains the full rule shape ({name, when:{type, max_usd, min_usd, reversible, target_ends_with}, verdict with enum values}) and the confirm flag's preview semantics, adding substantial meaning beyond the schema.

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+resource ("Save the user's rules") and even defines the rule format, so an agent immediately knows this persists approval rules. It does not explicitly name the sibling it complements (approve_get_rules), but the purpose is unambiguous and distinct from read-oriented siblings.

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 a concrete procedural workflow: call once without confirm to preview, then again with confirm=true, plus the auth prerequisite ("needs an API key so they stay yours"). It does not compare against alternatives like approve_get_rules, but the invocation guidance is clear and actionable.

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