Locus

Describe API

describe_api

Read-onlyIdempotent

Get one endpoint schema, example, output shape and price.

Input Schema

TableJSON Schema

Name	Required	Description
`slug`	Yes	provider/endpoint slug.
`model`	No	Exact fal model ID.
`model_cursor`	No	Fal page cursor.
`operation_query`	No	Search operations or fal/generate models.
`operation_offset`	No	MPP operation index or continuation offset.

Output Schema

TableJSON Schema

Name	Required	Description	Default
`slug`	No
`tool`	No
`title`	No
`inputSchema`	No

Schema Changelog

Changes observed during successful MCP inspections.

Changed5 schema fields changedOct 7, 2026
- removedOutput schema / additionalProperties
```
Removed value: -true
```
- removedOutput schema / properties / inputSchema / description
```
Removed value: -"JSON Schema for execute args."
```
- removedOutput schema / properties / slug / description
```
Removed value: -"provider/endpoint slug."
```
- removedOutput schema / properties / title / description
```
Removed value: -"Endpoint title."
```
- removedOutput schema / properties / tool / description
```
Removed value: -"Typed tool name for direct calls."
```

Changed3 schema fields changedSep 28, 2026

addedInput schema / properties / model

Added value: +{
+  "description": "Exact fal model ID.",
+  "maxLength": 240,
+  "type": "string"
+}

addedInput schema / properties / model_cursor

Added value: +{
+  "description": "Fal page cursor.",
+  "maxLength": 2048,
+  "type": "string"
+}

changedInput schema / properties / operation_query / description

Previous value: -"Search intent for directory operations."New value: +"Search operations or fal/generate models."

Changed2 schema fields changedSep 17, 2026

addedInput schema / properties / operation_query

Added value: +{
+  "description": "Search intent for directory operations.",
+  "maxLength": 256,
+  "type": "string"
+}

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "additionalProperties": true,
+  "properties": {
+    "inputSchema": {
+      "description": "JSON Schema for execute args.",
+      "type": "object"
+    },
+    "slug": {
+      "description": "provider/endpoint slug.",
+      "type": "string"
+    },
+    "title": {
+      "description": "Endpoint title.",
+      "type": "string"
+    },
+    "tool": {
+      "description": "Typed tool name for direct calls.",
+      "type": "string"
+    }
+  },
+  "type": "object"
+}

First observedSep 15, 2026

TDQS

B3.2/5.0

Behavior3/5

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

Annotations already establish readOnlyHint=true, idempotentHint=true, destructiveHint=false and a closed-world boundary, so the safety profile is covered. The description adds useful content disclosure (schema, example, output shape, price) but says nothing about rate limits, auth requirements, or the pagination/search behavior implied by the cursor and query parameters.

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

Conciseness4/5

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

A single front-loaded sentence with zero filler that enumerates the returned artifacts compactly. It is appropriately sized, though extremely terse for a five-parameter tool.

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

Completeness3/5

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

An output schema exists, so return values need no explanation, and annotations cover safety. However, the description omits usage context and leaves the four optional search/pagination parameters unexplained, so it is only just sufficient for a tool whose parameter set implies more than 'describe one endpoint'.

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

Parameters3/5

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

Schema description coverage is 100%, so the baseline of 3 applies; each parameter has at least a short description in the schema. The description adds no parameter meaning at all and does not clarify the non-obvious role of model_cursor, operation_query, and operation_offset, which suggest this tool also browses models/operations.

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?

States a specific verb ('Get') and resource ('one endpoint') plus the exact payload: schema, example, output shape and price. This distinguishes it from the plural search-oriented sibling search_apis, but the description never names that sibling or any other, so differentiation is inferred rather than stated.

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

Usage Guidelines2/5

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

There is no when-to-use guidance, no prerequisites, and no mention of alternatives such as search_apis (to find an endpoint) or execute (to run it). The agent must infer that this is an inspection step before execution.

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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