cost_trend

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

No annotations are provided, so the description must disclose behavioral traits. It mentions the output is a 'text chart' but does not clarify if the tool is read-only, whether it aggregates historical data, or any side effects (e.g., idempotency). The description is too minimal to inform safe usage.

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 extremely concise with two sentences, no superfluous words, and front-loads the core purpose. It includes an Args block for parameter documentation, which is efficient.

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 an output schema present, the return values need not be described, but the description lacks details on the chart format (e.g., ASCII art, data density) and any limitations. It is adequate for a simple tool but leaves gaps for an AI agent to understand full behavior.

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 schema has 0% description coverage, but the description explains the 'days' parameter as 'Number of days to show (default: 7)', adding meaning beyond the schema's type and default. This compensates well for the single parameter, improving usability.

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 the tool shows a daily spending trend as a text chart, which is a specific verb and resource. However, it does not distinguish from sibling tools like cost_report or estimate_cost, leaving ambiguity about when to use this particular tool.

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 guidance is provided on when to use this tool versus its siblings (cost_report, estimate_cost, etc.) or any exclusions. The description only states what the tool does, not the context of use.

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