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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), so the description's added value is its disclosure that data is returned as stored without recalculation and that a missing meter yields a tool error. That is meaningful beyond the annotations, though nothing is said about payload size or caching behavior.

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?

Three tight sentences, front-loaded with the action and key, followed by usage conditions and return behavior. No filler or repetition.

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 values need not be documented, yet the description still covers the notable return semantics (raw stored data) and the failure mode. Nothing needed to invoke this single-parameter tool correctly is missing.

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 coverage is 100%, so the baseline is 3, but the description adds real semantic constraints beyond the regex: the slug is exact and comes from list_meters/search_meters, and a UUID will not work. The schema's pattern only implies that prohibition.

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?

States a specific verb and resource ('Get one meter'), names the exact lookup key ('by its exact slug from list_meters'), and explicitly distinguishes itself from text search, which cleanly separates it from search_meters and list_meters.

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?

Gives an explicit when ('Use this when the slug is known') and a when-not ('this is not a text search'), which routes the agent to search_meters when no exact slug is available. Provenance of the slug is also specified.

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