Retrieve a capture by its ID to access standalone evidence for debugging or analysis, no upfront execution required. Link it to a run later.
Get a capture by id. Captures are standalone evidence; they don't need an execution upfront; link a capture to a run later with invariance_capture_link.
| Name | Required | Description | Default |
|---|---|---|---|
| id | Yes | Capture id, e.g. "cap_abc123". |
Changes observed during successful MCP inspections.
v0.3.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already carry readOnlyHint=true, so the safe-read behavior is covered. The description adds useful domain context about captures being standalone and linkable later, which goes beyond the annotations. However, it does not describe the return shape or behavior when the id is not found; with no output schema, that gap remains.
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 with no filler. The core operation is front-loaded, and the second sentence earns its place by explaining why captures differ from runs and naming the linking tool.
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 single-parameter read-only getter, the description is nearly complete: it defines the object being fetched, explains its standalone nature, and points to the follow-up action. The only minor gap is that no output format is described, but 'Get a capture' sufficiently implies the returned entity for this simple 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 description coverage is 100%: the single 'id' parameter is fully documented with a format example ('cap_abc123'). The description merely repeats the 'by id' usage without adding new parameter semantics, so the baseline of 3 applies.
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 states a specific verb and resource: 'Get a capture by id.' It also clarifies what a capture is ('standalone evidence') and distinguishes it from execution-bound entities like runs, helping an agent pick this over capture_list or run_get even among many siblings.
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 gives clear usage context: captures are standalone evidence that do not need an execution upfront, so this tool is for retrieving such a capture by id. It also names the related workflow step, invariance_capture_link, for later linking to a run. It stops short of explicitly contrasting this with capture_list or other retrieval tools, so it misses full exclusionary guidance.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.