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

Annotations already declare readOnlyHint=false, idempotentHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds one genuinely useful behavioral fact ('YABA never adds entries by itself'), which prevents a wrong assumption that marking creates transactions. It stops there, saying nothing about what marking actually changes (e.g. recurring plans or budget projections).

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 leading sentence is well front-loaded and the 'never adds entries' caveat earns its place. But two of the three sentences discuss amount minor-units and date formats for parameters that do not exist in this schema, so a substantial portion of the text is irrelevant noise for this tool.

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 mutating tool with three params (only cadence required) and no output schema, key details are missing: the txId/categoryId combination rule is unstated (the schema permits both or neither), and the relationship to unmark_bill is absent. An agent could invoke it, but could easily pick the wrong target combination.

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%, so the description must carry the load. It does clarify txId as an entry's payee and categoryId as a whole category, and the cadence enum values are self-explanatory. However, it never resolves whether txId and categoryId are mutually exclusive or that at least one is expected, and the amount/date formatting text maps to no parameter in this 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?

The description states a concrete action and its two modes: marking a single entry's payee (txId) or a whole category (categoryId) as a regular payment at a cadence. It adds the caveat that YABA never adds entries itself, which implicitly separates this from add_transaction. It does not name-mark against unmark_bill or dismiss_bill, so it stops short of full sibling differentiation.

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?

No when-to-use or when-not guidance is given. The inverse tool unmark_bill and the nearby dismiss_bill/list_bills are never referenced, so an agent has no stated basis for choosing this over them. The 'YABA never adds entries' line is a behavioral note, not usage guidance.

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