feat(agent): skill invocation — load and execute skills from catalog (#128) (#143)

Co-authored-by: Jason Woltje <jason@diversecanvas.com>
Co-committed-by: Jason Woltje <jason@diversecanvas.com>

apps/gateway/src/agent/tools/index.ts

@@ -4,3 +4,4 @@ export { createFileTools } from './file-tools.js';
 export { createGitTools } from './git-tools.js';
 export { createShellTools } from './shell-tools.js';
 export { createWebTools } from './web-tools.js';
+export { createSkillTools } from './skill-tools.js';

apps/gateway/src/agent/tools/skill-tools.ts

@@ -0,0 +1,180 @@
+import { Type } from '@sinclair/typebox';
+import type { ToolDefinition } from '@mariozechner/pi-coding-agent';
+import type { SkillsService } from '../../skills/skills.service.js';
+
+/**
+ * Creates meta-tools that allow agents to list and invoke skills from the catalog.
+ *
+ * skill_list  — list all enabled skills
+ * skill_invoke — execute a skill by name with parameters
+ */
+export function createSkillTools(skillsService: SkillsService): ToolDefinition[] {
+  const skillList: ToolDefinition = {
+    name: 'skill_list',
+    label: 'List Skills',
+    description:
+      'List all enabled skills available in the catalog. Returns name, description, type, and config for each skill.',
+    parameters: Type.Object({}),
+    async execute() {
+      const skills = await skillsService.findEnabled();
+      const summary = skills.map((s) => ({
+        name: s.name,
+        description: s.description,
+        version: s.version,
+        source: s.source,
+        config: s.config,
+      }));
+      return {
+        content: [
+          {
+            type: 'text' as const,
+            text:
+              summary.length > 0
+                ? JSON.stringify(summary, null, 2)
+                : 'No enabled skills found in catalog.',
+          },
+        ],
+        details: undefined,
+      };
+    },
+  };
+
+  const skillInvoke: ToolDefinition = {
+    name: 'skill_invoke',
+    label: 'Invoke Skill',
+    description:
+      'Invoke a skill from the catalog by name. For prompt skills, returns the prompt addition. ' +
+      'For tool skills, executes the embedded logic. For workflow skills, returns the workflow steps.',
+    parameters: Type.Object({
+      name: Type.String({ description: 'Skill name to invoke' }),
+      params: Type.Optional(
+        Type.Record(Type.String(), Type.Unknown(), {
+          description: 'Parameters to pass to the skill (if applicable)',
+        }),
+      ),
+    }),
+    async execute(_toolCallId, rawParams) {
+      const { name, params } = rawParams as {
+        name: string;
+        params?: Record<string, unknown>;
+      };
+
+      const skill = await skillsService.findByName(name);
+      if (!skill) {
+        return {
+          content: [{ type: 'text' as const, text: `Skill not found: ${name}` }],
+          details: undefined,
+        };
+      }
+
+      if (!skill.enabled) {
+        return {
+          content: [{ type: 'text' as const, text: `Skill is disabled: ${name}` }],
+          details: undefined,
+        };
+      }
+
+      const config = (skill.config ?? {}) as Record<string, unknown>;
+      const skillType = (config['type'] as string | undefined) ?? 'prompt';
+
+      switch (skillType) {
+        case 'prompt': {
+          const promptAddition =
+            (config['prompt'] as string | undefined) ?? skill.description ?? '';
+          return {
+            content: [
+              {
+                type: 'text' as const,
+                text: promptAddition
+                  ? `[Skill: ${name}] ${promptAddition}`
+                  : `[Skill: ${name}] No prompt content defined.`,
+              },
+            ],
+            details: undefined,
+          };
+        }
+
+        case 'tool': {
+          const toolLogic = config['logic'] as string | undefined;
+          if (!toolLogic) {
+            return {
+              content: [
+                {
+                  type: 'text' as const,
+                  text: `[Skill: ${name}] Tool skill has no logic defined.`,
+                },
+              ],
+              details: undefined,
+            };
+          }
+          // Inline tool skill execution: the logic field holds a JS expression or template
+          // For safety, treat it as a template that can reference params
+          const result = renderTemplate(toolLogic, { params: params ?? {}, skill });
+          return {
+            content: [{ type: 'text' as const, text: `[Skill: ${name}]\n${result}` }],
+            details: undefined,
+          };
+        }
+
+        case 'workflow': {
+          const steps = config['steps'] as unknown[] | undefined;
+          if (!steps || steps.length === 0) {
+            return {
+              content: [
+                {
+                  type: 'text' as const,
+                  text: `[Skill: ${name}] Workflow has no steps defined.`,
+                },
+              ],
+              details: undefined,
+            };
+          }
+          return {
+            content: [
+              {
+                type: 'text' as const,
+                text: `[Skill: ${name}] Workflow steps:\n${JSON.stringify(steps, null, 2)}`,
+              },
+            ],
+            details: undefined,
+          };
+        }
+
+        default: {
+          // Unknown type — return full config so the agent can decide what to do
+          return {
+            content: [
+              {
+                type: 'text' as const,
+                text: `[Skill: ${name}] (type: ${skillType})\n${JSON.stringify(config, null, 2)}`,
+              },
+            ],
+            details: undefined,
+          };
+        }
+      }
+    },
+  };
+
+  return [skillList, skillInvoke];
+}
+
+/**
+ * Minimal template renderer — replaces {{key}} with values from the context.
+ * Used for tool skill logic templates.
+ */
+function renderTemplate(template: string, context: Record<string, unknown>): string {
+  return template.replace(/\{\{(\w+(?:\.\w+)*)\}\}/g, (_match, path: string) => {
+    const parts = path.split('.');
+    let value: unknown = context;
+    for (const part of parts) {
+      if (value != null && typeof value === 'object') {
+        value = (value as Record<string, unknown>)[part];
+      } else {
+        value = undefined;
+        break;
+      }
+    }
+    return value !== undefined && value !== null ? String(value) : '';
+  });
+}