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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false. The description adds valuable behavioral details beyond those: search is case-insensitive substring, entity_type allows only one type, limit has a 1-2000 range, and names are verbatim (exact match). It also notes the historical depth aspect. No contradictions with annotations.

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 tight and well-structured: a one-sentence purpose, a usage directive, a note on `facets`, then a clean bulleted args list. It front-loads the most critical information (purpose and usage) and keeps each sentence purposeful. No fluff or redundancy.

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?

An output schema exists, so return-value details are already covered. The description supplies everything else needed to call the tool correctly: when to use it, how parameters behave, and the constraint that names are verbatim. It also hints at the `facets` output feature. The description is fully self-sufficient for an agent.

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 0%, so the description carries the full burden for parameter meaning. It explains each parameter with concrete examples: slug (the stream), search (case-insensitive substring with examples like 'HOUSTON'), entity_type (single type with enumerated examples), and limit (max count with range). This goes well beyond the bare schema titles and makes invocation error-prone-free.

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 looks up nodes, zones, stations, or fuels in a stream, and adds a specific behavior ('with how far back each goes'). It names the resource and verb explicitly, and distinguishes itself from query_stream by positioning itself as a prerequisite. This is a precise, unambiguous purpose.

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 gives explicit usage guidance: 'Use it before query_stream: names are verbatim and never to be guessed.' This tells the agent when to invoke this tool and why it matters for downstream use. It also mentions `facets` for counting, which aids selection. No alternatives are needed beyond this clear directive.

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