Lists distinct service names from traces whose earliest span falls within a specified UTC time window, enabling quick identification of services active in that period.
Distinct service.name values attached to traces whose earliest span falls inside the given UTC window. Sorted alphabetically.
| Name | Required | Description | Default |
|---|---|---|---|
| to | Yes | Window end (ISO-8601 UTC). Required, > from. | |
| from | Yes | Window start (ISO-8601 UTC). Required. |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint and idempotentHint, so safety is covered. The description adds real behavioral context beyond that: results are distinct service.name values, the window is evaluated against each trace's earliest span, and output is alphabetically sorted.
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, zero waste. The core operation is front-loaded and the ordering guarantee follows as a short trailing clause.
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?
With no output schema, the description compensates by describing what comes back (distinct service.name values, alphabetically sorted). The only minor gap is that no sibling or pagination/edge-case guidance is included, but nothing essential to correct invocation 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 both params are documented and a 3 baseline applies. The description goes beyond that by clarifying that the from/to window filters on the earliest span timestamp rather than any span, which is meaningful semantic information not present in the schema.
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+resource: distinct service.name values attached to traces, with the window defined by earliest span and an ordering guarantee. The word 'traces' implicitly distinguishes it from list_log_services and list_metric_services, though those siblings are never named explicitly.
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 scope statement ('traces whose earliest span falls inside the given UTC window') implies when the tool applies, but there is no explicit when-to-use or when-not guidance and no reference to query_traces or the sibling service-list tools as alternatives.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.