composio-skills-reference/composio-sdk/rules/app-modifiers.md

title, impact, description, tags

title	impact	description	tags
Tool Modifiers	MEDIUM	Advanced patterns for customizing tool behavior with schema modifications and execution hooks	modifiers hooks customization schema execution

Tool Modifiers

Modifiers customize tool behavior through schema transformations, pre-execution hooks, and post-execution hooks.

Schema Modification

Customize tool descriptions or parameters at fetch time:

const tools = await composio.tools.get(
  'default',
  { toolkits: ['github'] },
  {
    modifySchema: ({ toolSlug, toolkitSlug, schema }) => {
      // Enhance descriptions for AI
      schema.description = `[Enhanced] ${schema.description}`;

      // Customize specific parameters
      if (toolSlug === 'GITHUB_GET_REPO') {
        schema.inputParameters.properties.owner.description =
          'GitHub organization or user name (e.g., "composio")';
      }

      return schema;
    },
  }
);

Pre-Execution Hooks (beforeExecute)

Modify parameters before execution:

const result = await composio.tools.execute(
  'GITHUB_GET_REPO',
  {
    userId: 'default',
    arguments: { owner: 'Composio', repo: 'sdk' },
  },
  {
    beforeExecute: ({ toolSlug, params }) => {
      // Normalize inputs
      params.arguments.owner = params.arguments.owner.toLowerCase();

      // Add defaults
      params.arguments.branch = params.arguments.branch || 'main';

      return params;
    },
  }
);

Common uses:

• Parameter validation and normalization
• Adding default values
• Logging and tracing

Post-Execution Hooks (afterExecute)

Transform outputs after execution:

const result = await composio.tools.execute(
  'GITHUB_GET_REPO',
  {
    userId: 'default',
    arguments: { owner: 'composio', repo: 'sdk' },
  },
  {
    afterExecute: ({ result }) => {
      if (result.successful) {
        // Remove sensitive data
        delete result.data.token;

        // Add metadata
        result.data.fetchedAt = new Date().toISOString();
      }

      return result;
    },
  }
);

Common uses:

• Filtering sensitive data
• Data transformation and formatting
• Adding metadata

Common Patterns

Sensitive Data Filtering

const filterSensitive = ({ result }) => {
  if (result.successful) {
    ['token', 'secret', 'password', 'api_key'].forEach(field => {
      delete result.data[field];
    });
  }
  return result;
};

Logging & Monitoring

const monitor = {
  beforeExecute: ({ toolSlug, params }) => {
    console.log(`[START] ${toolSlug}`, params.arguments);
    return params;
  },
  afterExecute: ({ toolSlug, result }) => {
    console.log(`[END] ${toolSlug} - Success: ${result.successful}`);
    return result;
  },
};

Reusable Modifiers

const addTimestamps = ({ result }) => {
  if (result.successful) result.data.executedAt = new Date().toISOString();
  return result;
};

// Use in multiple executions
await composio.tools.execute('GITHUB_GET_REPO', { ... }, {
  afterExecute: addTimestamps
});

Key Points

• Schema modifiers apply at fetch time, execution modifiers at runtime
• Always return modified object (don't just mutate)
• Modifiers are synchronous - keep operations lightweight
• Must pass modifiers to each execute() call (not persisted)