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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so safety is covered. The description adds genuinely new behavioral context that annotations cannot carry: amount units (minor units, 45000 = 450.00), date format and the family time zone, and what a 'month' means (budget period YYYY-MM). It stops short of describing volume, ordering, or pagination.

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 sentences, no filler, with the returned-field inventory front-loaded and format rules consolidated into a second sentence. The opening clause is slightly run-on and the 'YABA found or someone marked' phrasing costs a moment of parsing, but nothing is wasted.

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 no input parameters, the description carries the full documentation burden and does so: it lists the returned fields, explains the units and date/time-zone conventions, and points at the follow-up tools that consume the key. Missing only ordering/pagination and the exact shape of the key field, which are minor for this tool.

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?

The tool takes zero parameters, so the baseline is 4. The description compensates by documenting the value formats an agent needs to interpret results (minor-unit amounts, YYYY-MM-DD dates, YYYY-MM budget periods), which is the relevant semantic detail for a no-arg list tool.

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 enumerates what the tool returns (recurring payments and income, detected automatically or manually marked) and the fields each entry carries, so an agent can infer it is a read/list tool for recurring bills. It lacks a clean verb+resource opener (the name 'list_bills' isn't restated, and 'YABA found or someone marked' is grammatically murky), but the resource is unambiguous and it distinguishes itself from siblings by naming the key consumed by dismiss_bill/unmark_bill.

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?

Usage is only implied: the mention of 'the key to use with dismiss_bill / unmark_bill' signals this is the discovery step before those mutation tools, but there is no explicit when-to-use statement, no exclusions, and no comparison against sibling list/mark tools like list_transactions or mark_bill.

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