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

With no annotations provided, the description carries the transparency burden. It discloses a key behavioral quirk: 'Services with no archive are listed separately as uncovered instead of being ranked as flawless.' It also lists the output metrics, but it does not specify the exact ranking algorithm or how the window affects each metric, leaving some ambiguity.

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 at just two sentences, front-loaded with the core function and output. The first sentence defines the return value, the second gives usage guidance and a special case. No filler words; every sentence earns its place.

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 two parameters and no output schema, the description covers the essential output (scorecard with four reliability metrics) and mentions a notable edge case. However, it does not fully specify the ranking order ('worst-first' could be by downtime or incident count) or response format, leaving some gaps for a tool of this simplicity.

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 already provides descriptions for both parameters (services array and window enum), so coverage is 100%. The description adds minimal semantic value beyond the schema, mostly reinforcing that services are slugs and referring to 'a window'. This is sufficient but not exceptional, aligning with the baseline for high schema coverage.

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 function: 'Given several service slugs, return a scorecard ranked worst-first' and enumerates the metrics (incident count, downtime, MTTR, longest incident). It also distinguishes itself from siblings by emphasizing cross-vendor comparison, which vendor monitoring tools cannot do.

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 explicitly provides a use case: 'Use this to answer "which vendor in my stack is least reliable?"' and notes that it compares services across vendors, differentiating it from single-vendor monitoring alternatives. Although no sibling tools are named, the context makes the appropriate usage clear.

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