Payees — List

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

Annotations already declare readOnlyHint=true, openWorldHint=false and destructiveHint=false, so safety is covered. The description adds genuinely non-obvious behavior: incremental/delta retrieval semantics and the meaning of the server_knowledge token, which an agent could not infer from the schema.

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?

Front-loaded with the core action and the delta-sync mechanic immediately after. The closing sentence on changes_since is somewhat tangential for a payees tool but earns its place as a routing hint; otherwise the text is tight.

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 description still usefully ties last_knowledge_of_server back to the server_knowledge value in responses. Only the plan_id default and behavior when omitted are left unaddressed.

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 0% with 2 parameters, so the description carries the burden. It compensates well for last_knowledge_of_server (origin of the value, effect on the response), but plan_id is never mentioned and its null default is unexplained. Partial compensation justifies the baseline 3.

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 ('List all payees for a plan') with the [READ] marker, which is enough to distinguish it from payees_get, payee_locations_list, and transactions_list_by_payee. It does not explicitly name the sibling it is not, so it stops short of a 5.

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?

Explains the condition for using the delta-sync parameter ('pass last_knowledge_of_server ... and YNAB sends only what changed since') and points at changes_since as the cross-resource alternative. It gives clear context but no explicit exclusions or a when-not-to-use statement.

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