Run an instant PromQL query against Prometheus to retrieve metric values at a single point in time.
Execute an instant Prometheus query
| Name | Required | Description | Default |
|---|---|---|---|
| time | No | Evaluation timestamp (RFC3339 or Unix timestamp) | |
| query | Yes | PromQL query expression | |
| timeout | No | Evaluation timeout (e.g. '30s') |
Changes observed during successful MCP inspections.
v1.0.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations provided, the description carries the full burden of behavioral disclosure. While 'Execute' implies an operation that might have side effects or performance implications, the description doesn't mention whether this is a read-only operation, what authentication might be required, potential rate limits, or what happens when queries fail. For a query execution tool with zero annotation coverage, this is a significant gap.
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 extremely concise at just 5 words, front-loading the essential information with zero wasted words. Every element ('Execute', 'instant', 'Prometheus query') earns its place in communicating the core functionality.
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?
For a query execution tool with no annotations and no output schema, the description is insufficiently complete. It doesn't explain what an 'instant' query means in Prometheus context, what format the results will be in, or any error conditions. Given the complexity of query execution and the lack of structured metadata, the description should provide more operational context.
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 description coverage is 100%, meaning all parameters are well-documented in the input schema itself. The description doesn't add any additional parameter semantics beyond what's already in the schema descriptions. This meets the baseline expectation when schema coverage is high, but doesn't provide extra value.
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 action ('Execute') and resource ('an instant Prometheus query'), making the purpose immediately understandable. However, it doesn't differentiate this tool from its sibling 'range-query' tool, which appears to be a closely related alternative for querying Prometheus data with a different time range approach.
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 no guidance on when to use this tool versus alternatives like 'range-query' or other Prometheus querying tools. There's no mention of what makes an 'instant' query different from other query types, nor any prerequisites or context for when this specific tool is appropriate.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.