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

Annotations already declare readOnly/idempotent/non-destructive, so safety is covered. The description goes beyond them by disclosing how results are derived (3+ occurrences = active, twice = suggested, stopped = ended) and by explicitly excluding payroll and transfers from detection, which materially shapes interpretation of the output.

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?

A single dense paragraph that front-loads what the tool returns, then the status legend, then the exclusion. Every clause carries information, though the long comma list of returned attributes is slightly harder to scan than a structured breakdown would be.

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, the description usefully enumerates the returned fields, and all four parameters are documented in the schema. It omits any mention of result limits, pagination, or ordering, which an agent might need for a potentially long list of detected merchants.

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. The description adds value above that by defining the enum values of `status` in business terms and clarifying that 'active' means counted in bills due, which the schema alone does not convey.

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 concrete resource (subscriptions and recurring bills detected from bank/card charges) and enumerates the specific attributes returned (price, frequency, next expected charge, late flag, price changes, converted trials). An agent can distinguish this from siblings like list_upcoming or get_payroll without reading the schema.

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 description explains the meaning of each status value (active = seen 3+ times and counted in bills due, suggested = seen twice, ended = stopped), which implicitly guides filter choice, and rules out payroll/transfers as content. However, it never states when to pick this tool over the adjacent sibling list_upcoming, leaving tool selection partly to inference.

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