rum

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

No annotations provided, so the description carries full burden. It describes the tool as querying data and performing actions like aggregate, performance, and waterfall, which suggests read-only behavior. However, it does not explicitly state idempotency, rate limits, or authentication requirements. The lack of contradiction with annotations is fine, but more detail on behavioral traits would improve transparency.

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 concise: a single paragraph with a clear structure—first sentence defines purpose, then a bullet-like list of actions with brief explanations, finally a sentence on use cases. No redundant information, and every sentence adds value.

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's complexity (13 parameters, no output schema), the description provides a solid overview of actions and use cases. It explains each action's purpose and mentions key metrics (Core Web Vitals). However, it could be more complete by explicitly stating the tool is read-only and how to construct queries for different actions.

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 value by explaining actions (e.g., 'Core Web Vitals: LCP, FCP, CLS, FID, INP') and giving examples for query syntax. It also describes the 'waterfall' action as 'session timeline with resources/actions/errors', which provides context beyond the schema's parameter descriptions.

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 queries Datadog RUM data and lists specific actions with their purposes (e.g., 'applications (list RUM apps)', 'events (search RUM events)'). It distinguishes from sibling tools by focusing on frontend performance, user sessions, page views, errors, and resource loading, which are unique to RUM.

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 provides clear context for usage: 'Use for: frontend performance, user sessions, page views, errors, resource loading.' It does not explicitly state when not to use or compare to alternatives, but the listed use cases and sibling tools (logs, metrics) imply the tool's domain.

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