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

Annotations only declare a non-read-only, non-destructive mutation; the description carries the real behavioral burden. It discloses the dry-run versus apply semantics, immediate effect on future transactions, the gated Recalculate card for past-period adjustments, that nothing is backdated through this tool, and the ERP-posted refusal condition.

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 description is dense but front-loaded: it first states what changes, then units, then the dry-run/apply protocol, then side effects and refusals. Every sentence adds operational value, with no repetition of the schema's property descriptions beyond essential unit conventions.

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 mutation tool with no output schema, the description covers the full calling workflow, side effects, approval gating, refusal conditions, account prerequisite, and scope limits. An agent has enough to decide whether to dry-run, apply, or use the supersede path instead.

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%, so the baseline is 3, but the description adds useful semantics: rates are in percent (1.5 = 1.5%) and thresholds in dollars, and a no-edit dry run lists current regimes with their keys and rates. The parameter-level schema already documents confirm, regimes, and shared_tier_grid, so the description is reinforcing rather than the primary source.

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 (change rates on a rate-routed agreement) and explicitly distinguishes what is editable (rates) from what is not (routing dimension, regime keys, member values). It also distinguishes which kind of rate is targeted: flat, regime-specific tiers, or the shared tier ladder.

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?

Explicitly prescribes the two-step workflow: call without confirm to dry-run and list or echo, then call with confirm:true to apply. It also states a clear exclusion — 'Refuses if posted to the ERP (supersede instead)' — and notes the connected-account requirement, leaving little to inference.

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