Licium

Call an explicitly selected capability

capability_call

Call one capability by id at its listed price. Available referral credit is applied automatically first. payment_path x402 needs agent_key; balance needs agent_key or api_key; upstream needs agent_key, parent_call_id, and composition_token, is charged to the parent supplier, and is one level only. A 402 challenge is returned as data. Unpaid x402 reservations expire after one hour; retry with a new idempotency_key.

Input Schema

TableJSON Schema

Name	Required	Description
`input`	Yes
`api_key`	No	Optional alternative to agent_key for balance calls.
`agent_key`	No	Required for x402 and upstream.
`payment_path`	Yes
`capability_id`	Yes	Explicit capability UUID.
`parent_call_id`	No	Required for upstream.
`idempotency_key`	Yes
`composition_token`	No	Required for upstream; supplied to the parent capability endpoint for this dispatch.
`idempotent_replay`	No	Set true only for an explicit same-call-id replay after an uncertain upstream dispatch.

Schema Changelog

Changes observed during successful MCP inspections.

Changed7 schema fields changedOct 1, 2026

addedInput schema / additionalProperties
```
Added value: +false
```

changedInput schema / properties / agent_key / description

Previous value: -"Required for x402."New value: +"Required for x402 and upstream."

changedInput schema / properties / api_key / description

Previous value: -"Required for balance calls outside a browser session."New value: +"Optional alternative to agent_key for balance calls."

addedInput schema / properties / composition_token

Added value: +{
+  "description": "Required for upstream; supplied to the parent capability endpoint for this dispatch.",
+  "maxLength": 2048,
+  "minLength": 32,
+  "type": "string"
+}

addedInput schema / properties / idempotent_replay

Added value: +{
+  "description": "Set true only for an explicit same-call-id replay after an uncertain upstream dispatch.",
+  "type": "boolean"
+}

addedInput schema / properties / parent_call_id

Added value: +{
+  "description": "Required for upstream.",
+  "format": "uuid",
+  "type": "string"
+}

changedInput schema / properties / payment_path / enum

Previous value: -[
-  "x402",
-  "balance"
-]New value: +[
+  "x402",
+  "balance",
+  "upstream"
+]

AddedAug 17, 2026

TDQS

A4.6/5.0

Behavior5/5

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

With no annotations, the description carries the full burden and delivers rich behavioral detail: referral credit is applied automatically, upstream calls are charged to the parent supplier and restricted to one level, 402 challenges are returned as data, unpaid x402 reservations expire after one hour, and retries require a new idempotency_key. This covers auth needs, side effects, error handling, and expiry semantics.

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 five dense sentences, each contributing essential information. The main purpose is front-loaded, and subsequent sentences cover credit application, payment path requirements, error handling, and retry logic without any filler.

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

Completeness4/5

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

For a complex tool with 9 parameters, no annotations, and no output schema, the description covers payment flows, expiry, retry, and error responses well. It leaves gaps in describing the 'input' payload format and success return behavior, but the critical invocation mechanics are present.

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

Parameters4/5

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

Schema description coverage is 67%, and the description adds meaningful semantics beyond it, especially for payment_path (mapping each enum value to required credentials and charging behavior). It also clarifies cross-parameter dependencies for upstream. However, the required 'input' parameter remains completely undocumented in both schema and description.

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

Purpose5/5

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

The description states a specific verb and resource: 'Call one capability by id at its listed price.' This clearly distinguishes it from sibling tools like capability_get (retrieve details) and capabilities_list (enumerate). The agent can immediately tell this is the execution/invocation action.

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

Usage Guidelines4/5

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

It provides clear context for each payment_path: x402 needs agent_key, balance needs agent_key or api_key, upstream needs agent_key, parent_call_id, and composition_token, with charging to the parent supplier and a one-level limit. However, it does not explicitly state when to choose this tool over alternatives or include exclusions about sibling tools.

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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