cos_metric_trend

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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, establishing a safe read-only operation. The description adds parameter constraints (metric allowed values, window range 1-365, group_by options) and the return structure (trends array with period, counts, rate), which goes beyond the annotations and enriches behavioral understanding.

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 compact and well-organized with a clear Args/Returns layout. Every sentence provides essential information, and there is no redundant or verbose content.

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 read-only query tool with three parameters and an existing output schema, the description sufficiently covers inputs and the high-level return shape. It could add an example or clarify the meaning of 'period' in the trends array, but overall it is complete and actionable.

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 descriptions are absent (0% coverage), so the description fully compensates by enumerating all three parameters, their allowed values, defaults, and semantics. For example, it specifies that window_days is a lookback window (1-365, default 30) and groups by domain, model, agent_type, or complexity, making the tool immediately usable.

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 opens with 'Get aggregated trend data for agent metrics,' clearly indicating a specific verb (get) and resource (agent metrics) with a focus on trends. This differentiates it from sibling tools like cos_metric_query and cos_metric_record, which likely handle direct lookups or recording.

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 use case is implied by the purpose—aggregated trend analysis—but the description does not explicitly state when to use this tool versus alternatives, nor does it mention exclusions or prerequisites. It provides no guidance on choosing between this and similar metric tools.

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