CreatePayee

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

Annotations already declare readOnlyHint=false, idempotentHint=false, destructiveHint=false and openWorldHint=true, so the safety and repeat-call profile is covered structurally. The description adds the cross-tool behavioral note that CreateTransaction can create a payee too, which is useful, but it does not disclose what happens on duplicate names, whether a plan must be writable, or what is returned. Given the annotation coverage, 3 is appropriate.

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 short sentences, zero waste, purpose front-loaded and the alternative-path note parenthesized so it does not obscure the primary statement.

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?

An output schema exists, so return values need no explanation, and the parameter surface is fully documented in the schema. However, for a creation tool the description is silent on duplicate-payee behavior and on the relationship to Ynab_UpdatePayee, leaving gaps an agent would want filled before calling.

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 (name, plan_id) are documented in the schema, including the 'last-used' default and the ListPlans pointer. The description adds nothing beyond the schema, so the baseline of 3 applies.

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?

Specific verb+resource: 'Create a payee.' It also flags the overlap with Ynab_CreateTransaction, which lets an agent distinguish this tool from the most plausible alternative. It stops short of distinguishing from Ynab_UpdatePayee or explaining scope relative to plan_id, but the core purpose is unambiguous.

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 parenthetical hints at an alternative route (creating a payee implicitly via CreateTransaction's payee_name), which implies a when-you-might-not-need-this condition, but it is not framed as guidance. There is no explicit statement of when to call this versus Ynab_UpdatePayee or when to prefer the implicit path, nor any prerequisites.

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