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

Annotations already cover read-only/idempotent/non-destructive, and the description goes beyond them usefully: savings are estimates relative to typical local prices, totals count ranged lines only while thin and unranged lines are counted separately, and the tool is free including after the trial. The main missing behavior is whether date defaults apply or how pagination/interaction with linesLimit affects totals.

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 resource name and the summary cue are front-loaded, but the body is one long run-on sentence with backtick field names strung together by commas, which is hard to parse. The content mostly earns its place, but it would read far better as a short paragraph plus a field list.

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?

There is no output schema, so the description carries the return-value burden and does it well by enumerating every field including method/methodUrl. However, for a tool with date-range parameters and a line cap, the absence of any explanation of how from/to/linesLimit scope the result leaves a real gap in an otherwise rich definition.

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 only 33%: only linesLimit is described in the schema. The description never mentions to, from, or linesLimit, so an agent gets no explanation of the date-range filtering, defaults, or that linesLimit caps the detailed lines without changing totals. It does not compensate for the coverage gap.

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 specific resource ('the running savings record') and enumerates its contents (vsTypical, vsCheapest, vsPriciest, totals by flyer week/month, best/worst lines, summary, shareable, method). That is far more specific than the title 'The user's savings record' alone. It never names a sibling tool (e.g., price_history, compare_items) to differentiate, 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?

Guidance is present but indirect: 'summary (lead with this...)' and 'shareable... to give the user when they ask' tell the agent how to use outputs, and 'positive = under typical' explains the sign convention. There is no statement of when to call this versus siblings like price_history or compare_items, and no prerequisites or exclusions.

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