forecast_monthly_cost

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

No annotations are provided, so the description carries full burden. It discloses that the tool returns a per-provider projection and confidence note and suggests re-running for stability, but does not explicitly state whether the operation is read-only or discuss any side effects or permissions needed.

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 description is three short, front-loaded sentences with no filler. Each sentence adds value: purpose, return structure, and usage advice. It is efficient and well-structured.

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 tool with one optional parameter and no output schema, the description adequately covers what it does and returns (per-provider projection, confidence note). It is mostly complete, though it could specify the format of the projection or confidence level more precisely.

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 input schema already provides 100% coverage (window_hours with description and default). The description adds no new parameter meaning beyond the schema, only context about stability. Baseline 3 is appropriate as the description does not detract but adds minimal extra value.

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 clearly states the tool projects 30-day total spend from observed run rate, with a specific verb ('projects') and resource ('30-day total spend'). It distinguishes from sibling tools like cost_overview or costs_by_provider by focusing on forecasting rather than current breakdowns.

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 advises re-running with a longer window for stability, implying when to adjust the parameter, but it does not explicitly state when to use this tool versus alternatives like find_cost_anomalies or top_cost_drivers. No when-not or comparator guidance is provided.

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