Retrieve the active fixture backend info and its limitations to assess current setup constraints.
Describe the active fixture backend and its limitations
| Name | Required | Description | Default |
|---|---|---|---|
No arguments | |||
| Name | Required | Description | Default |
|---|---|---|---|
| ok | Yes | ||
| data | No | ||
| live | No | ||
| tool | Yes | ||
| error | No | ||
| receipt | No | ||
| documentRevision | No | ||
| operationFingerprint | No |
Changes observed during successful MCP inspections.
v0.3.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already disclose readOnly, idempotent, and non-destructive behavior, so the bar for additional disclosure is lower. The description adds that the output will cover limitations, which gives some context about the nature of the result, but it doesn't elaborate on side effects, prerequisites, or other behavioral traits beyond what annotations already cover.
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 a single, tightly written sentence that states the core purpose and the added value ('limitations') without any fluff. Every word earns its place, and the key resource is front-loaded.
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 zero-parameter tool with a rich output schema and safety annotations, the description is nearly sufficient. The only minor gap is that 'limitations' is left ambiguous – it could be clarified whether these are limitations of the fixture backend's capabilities, accuracy, or something else – but this is a small concern given the output schema will define the structure.
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 tool has zero parameters, and schema coverage is 100% (empty schema), so there are no parameter semantics to explain. Per the baseline rule for zero-parameter tools, a score of 4 is appropriate; the description doesn't need to add anything about inputs.
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 uses a specific verb ('Describe') with a clear resource ('the active fixture backend') and adds a distinctive qualifier ('and its limitations'). It is immediately distinguishable from all sibling tools, none of which reference fixtures, so an agent can select it confidently.
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 explicit guidance on when to invoke this tool versus alternatives. There are no conditions, alternatives named, or exclusions given; the agent must infer that it should be used when fixture backend information is needed, which is implied but not stated.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.