Discover what you can pass to get_metrics / get_histogram: filter keys, group_by values, built-in metrics, and contract metric paths (optional kind filter). Call this when unsure of a key or path.
| Name | Required | Description | Default |
|---|---|---|---|
| kind | No | Optional contract kind: scalar, boolean, categorical, set, weighted_set, measures. | |
| include_paths | No | Include full contract path list. Default true. |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true and destructiveHint=false. Description adds that it returns a list of options for other calls, providing useful behavioral context beyond 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?
Two sentences, front-loaded with action and result, no wasted words. Efficient and clear.
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 no output schema, the description adequately explains the return value (list of keys, paths, etc.). It provides context of when to use and what parameters are available. Complete for a simple discovery tool.
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% with descriptions for both params. The description adds minimal parameter info beyond mentioning an optional kind filter; it mostly focuses on the output. Baseline of 3 is appropriate.
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?
Description clearly states the verb 'discover' and the resource 'options for get_metrics/get_histogram', listing specific items it returns (filter keys, group_by values, etc.). It distinguishes from sibling tools by being a helper for them.
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?
Explicitly says 'Call this when unsure of a key or path', providing clear when-to-use advice. It does not explicitly exclude cases but the context is clear enough.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Add one secure layer between your agents and this server.
Each tool has a clearly distinct purpose: get_histogram returns histogram buckets for one metric, get_metrics returns aggregate stats with optional grouping, and list_options provides metadata. No confusion possible.
All tool names follow a consistent verb_noun pattern (get_histogram, get_metrics, list_options) using snake_case, which is predictable and clear.
Three tools is well-scoped for a web vitals query API. Each tool earns its place: data retrieval, histogram analysis, and options discovery. No unnecessary bloat.
The tool set covers all necessary operations for the domain: aggregate metrics, detailed distribution (histogram), and parameter discovery. No obvious gaps like missing time-series or comparison features, but the stated purpose is sufficiently served.
