cost_trend

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

Annotations already provide readOnlyHint: true and destructiveHint: false, so the description carries less burden. It adds value by stating returns 'monthly cost data points' and the optional breakdown. No contradictions. The description could mention auth or rate limits, but annotations cover safety, so a small deduction is appropriate.

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 two sentences, front-loaded with purpose and examples. Every sentence is valuable and non-redundant. It achieves high information density without waste.

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?

Given the tool has 4 optional parameters and no output schema, the description adequately explains the output ('monthly cost data points, optionally broken down'). It covers the main use case and distinguishes from siblings. Minor gap: could mention the default months=6 explicitly, but the schema already has a default.

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 baseline is 3. The description adds minimal extra meaning: it mentions 'optionally broken down by service/project/cloud' which maps to groupBy, but the schema already describes it. The usage context is slightly enriched but not enough to raise the score above baseline.

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's purpose: to show monthly spend over time. It uses specific verbs ('see', 'returns') and identifies the resource ('monthly cost data points'). The examples ('Show me my cost trend') make it concrete. It also distinguishes from sibling tools by noting the alternative for daily/custom intervals.

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?

Explicit when-to-use guidance with examples ('when the user wants to see monthly spend over time'). Explicit when-not-to-use: 'For daily granularity or custom time intervals, use run_query instead.' This is a clear alternative, satisfying the highest level of this dimension.

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