pix-mcp

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pix_collect_counters

Read-onlyIdempotent

Collects per-event counter values from a PIX capture by replaying it, using exact counter names or regex patterns for matching.

Instructions

Replay the capture collecting counters, returning per-event counter values.

counters takes exact names from pix_list_counters and escapes them. Use counter_regexes to match families, remembering that every counter matched is another replay pass over the capture.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "capture_id": "<capture_id>"
    },
    "name": "pix_collect_counters"
  }
}

Input Schema

Name	Required	Description	Default
`limit`	No
`cursor`	No
`refresh`	No
`counters`	No
`capture_id`	Yes
`queue_name`	No
`counter_groups`	No
`counter_regexes`	No
`timeout_seconds`	No

Output Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Sep 9, 2026

TDQS

B3.4/5.0

Behavior4/5

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

Annotations already mark the tool as read-only, idempotent, and non-destructive. The description adds valuable behavioral context beyond annotations: it reveals that the tool replays the capture, that counter names must be escaped exact names, and that matching multiple regexes means multiple replay passes. This performance cost is important for an agent to know before invocation.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is compact and front-loaded: the first sentence states the core purpose, followed by the most important parameter usage notes and a cost caveat. Every sentence earns its place, with no redundant restatement of the tool name or schema properties.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness2/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

This is a 9-parameter tool with no schema-level parameter descriptions, and the tool description only covers two of those parameters plus a performance warning. While the output schema may document return values, the input semantics for pagination, queueing, refresh behavior, and timeouts are missing, leaving the agent under-informed for correct invocation.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters2/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

With 0% schema description coverage, the description must compensate for undocumented parameters. It explains 'counters' and 'counter_regexes', but says nothing about capture_id, limit, cursor, refresh, queue_name, counter_groups, or timeout_seconds. The schema provides only names and defaults, so most parameters remain semantically opaque to the agent.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states that the tool replays a capture and collects counters, returning per-event values. This is a specific action with a clear resource and output. It does not explicitly name sibling tools, but the 'per-event counter values' phrasing helps distinguish it from counter-listing tools like pix_list_counters.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description gives operational guidance on how to specify counters using exact names from pix_list_counters or regex families, and warns that each regex match costs an additional replay pass. However, it does not explicitly state when to use this tool versus alternatives like pix_get_counter_hotspots or pix_list_counters, leaving the selection mostly implied.

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

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