diff --git a/src/github/operations/pulls.ts b/src/github/operations/pulls.ts
index 34ae85d2..49084c94 100644
--- a/src/github/operations/pulls.ts
+++ b/src/github/operations/pulls.ts
@@ -5,71 +5,122 @@ import {
   GitHubRepositorySchema 
 } from "../common/types.js";
 
-// Schema definitions
-export const GitHubPullRequestHeadSchema = z.object({
+// Constants for GitHub limits and constraints
+const GITHUB_TITLE_MAX_LENGTH = 256;
+const GITHUB_BODY_MAX_LENGTH = 65536;
+
+// Base schema for repository identification
+export const RepositoryParamsSchema = z.object({
+  owner: z.string().min(1).describe("Repository owner (username or organization)"),
+  repo: z.string().min(1).describe("Repository name"),
+});
+
+// Common validation schemas
+export const GitHubPullRequestStateSchema = z.enum([
+  "open",
+  "closed",
+  "merged",
+  "draft"
+]).describe("The current state of the pull request");
+
+export const GitHubPullRequestSortSchema = z.enum([
+  "created",
+  "updated",
+  "popularity",
+  "long-running"
+]).describe("The sorting field for pull requests");
+
+export const GitHubDirectionSchema = z.enum([
+  "asc",
+  "desc"
+]).describe("The sort direction");
+
+// Pull request head/base schema
+export const GitHubPullRequestRefSchema = z.object({
   label: z.string(),
-  ref: z.string(),
-  sha: z.string(),
+  ref: z.string().min(1),
+  sha: z.string().length(40),
   user: GitHubIssueAssigneeSchema,
   repo: GitHubRepositorySchema,
-});
+}).describe("Reference information for pull request head or base");
 
+// Main pull request schema
 export const GitHubPullRequestSchema = z.object({
-  url: z.string(),
-  id: z.number(),
+  url: z.string().url(),
+  id: z.number().positive(),
   node_id: z.string(),
-  html_url: z.string(),
-  diff_url: z.string(),
-  patch_url: z.string(),
-  issue_url: z.string(),
-  number: z.number(),
-  state: z.string(),
+  html_url: z.string().url(),
+  diff_url: z.string().url(),
+  patch_url: z.string().url(),
+  issue_url: z.string().url(),
+  number: z.number().positive(),
+  state: GitHubPullRequestStateSchema,
   locked: z.boolean(),
-  title: z.string(),
+  title: z.string().max(GITHUB_TITLE_MAX_LENGTH),
   user: GitHubIssueAssigneeSchema,
-  body: z.string(),
-  created_at: z.string(),
-  updated_at: z.string(),
-  closed_at: z.string().nullable(),
-  merged_at: z.string().nullable(),
-  merge_commit_sha: z.string().nullable(),
+  body: z.string().max(GITHUB_BODY_MAX_LENGTH).nullable(),
+  created_at: z.string().datetime(),
+  updated_at: z.string().datetime(),
+  closed_at: z.string().datetime().nullable(),
+  merged_at: z.string().datetime().nullable(),
+  merge_commit_sha: z.string().length(40).nullable(),
   assignee: GitHubIssueAssigneeSchema.nullable(),
   assignees: z.array(GitHubIssueAssigneeSchema),
-  head: GitHubPullRequestHeadSchema,
-  base: GitHubPullRequestHeadSchema,
+  requested_reviewers: z.array(GitHubIssueAssigneeSchema),
+  labels: z.array(z.object({
+    name: z.string(),
+    color: z.string().regex(/^[0-9a-fA-F]{6}$/),
+    description: z.string().nullable(),
+  })),
+  head: GitHubPullRequestRefSchema,
+  base: GitHubPullRequestRefSchema,
 });
 
+// Request schemas
+export const ListPullRequestsOptionsSchema = z.object({
+  state: GitHubPullRequestStateSchema.optional(),
+  head: z.string().optional(),
+  base: z.string().optional(),
+  sort: GitHubPullRequestSortSchema.optional(),
+  direction: GitHubDirectionSchema.optional(),
+  per_page: z.number().min(1).max(100).optional(),
+  page: z.number().min(1).optional(),
+}).describe("Options for listing pull requests");
+
 export const CreatePullRequestOptionsSchema = z.object({
-  title: z.string().describe("Pull request title"),
-  body: z.string().optional().describe("Pull request body/description"),
-  head: z.string().describe("The name of the branch where your changes are implemented"),
-  base: z.string().describe("The name of the branch you want the changes pulled into"),
+  title: z.string().max(GITHUB_TITLE_MAX_LENGTH).describe("Pull request title"),
+  body: z.string().max(GITHUB_BODY_MAX_LENGTH).optional().describe("Pull request body/description"),
+  head: z.string().min(1).describe("The name of the branch where your changes are implemented"),
+  base: z.string().min(1).describe("The name of the branch you want the changes pulled into"),
   maintainer_can_modify: z.boolean().optional().describe("Whether maintainers can modify the pull request"),
   draft: z.boolean().optional().describe("Whether to create the pull request as a draft"),
-});
+}).describe("Options for creating a pull request");
 
-export const CreatePullRequestSchema = z.object({
-  owner: z.string().describe("Repository owner (username or organization)"),
-  repo: z.string().describe("Repository name"),
-  title: z.string().describe("Pull request title"),
-  body: z.string().optional().describe("Pull request body/description"),
-  head: z.string().describe("The name of the branch where your changes are implemented"),
-  base: z.string().describe("The name of the branch you want the changes pulled into"),
-  draft: z.boolean().optional().describe("Whether to create the pull request as a draft"),
-  maintainer_can_modify: z.boolean().optional().describe("Whether maintainers can modify the pull request"),
+// Combine repository params with operation options
+export const CreatePullRequestSchema = RepositoryParamsSchema.extend({
+  ...CreatePullRequestOptionsSchema.shape,
 });
 
 // Type exports
+export type RepositoryParams = z.infer<typeof RepositoryParamsSchema>;
 export type CreatePullRequestOptions = z.infer<typeof CreatePullRequestOptionsSchema>;
+export type ListPullRequestsOptions = z.infer<typeof ListPullRequestsOptionsSchema>;
 export type GitHubPullRequest = z.infer<typeof GitHubPullRequestSchema>;
-export type GitHubPullRequestHead = z.infer<typeof GitHubPullRequestHeadSchema>;
+export type GitHubPullRequestRef = z.infer<typeof GitHubPullRequestRefSchema>;
 
-// Function implementations
+/**
+ * Creates a new pull request in a repository.
+ * 
+ * @param params Repository identification and pull request creation options
+ * @returns Promise resolving to the created pull request
+ * @throws {ZodError} If the input parameters fail validation
+ * @throws {Error} If the GitHub API request fails
+ */
 export async function createPullRequest(
-  owner: string,
-  repo: string,
-  options: CreatePullRequestOptions
-): Promise<z.infer<typeof GitHubPullRequestSchema>> {
+  params: z.infer<typeof CreatePullRequestSchema>
+): Promise<GitHubPullRequest> {
+  const { owner, repo, ...options } = CreatePullRequestSchema.parse(params);
+  
   const response = await githubRequest(
     `https://api.github.com/repos/${owner}/${repo}/pulls`,
     {
@@ -81,11 +132,21 @@ export async function createPullRequest(
   return GitHubPullRequestSchema.parse(response);
 }
 
+/**
+ * Retrieves a specific pull request by its number.
+ * 
+ * @param params Repository parameters and pull request number
+ * @returns Promise resolving to the pull request details
+ * @throws {Error} If the pull request is not found or the request fails
+ */
 export async function getPullRequest(
-  owner: string,
-  repo: string,
-  pullNumber: number
-): Promise<z.infer<typeof GitHubPullRequestSchema>> {
+  params: RepositoryParams & { pullNumber: number }
+): Promise<GitHubPullRequest> {
+  const { owner, repo, pullNumber } = z.object({
+    ...RepositoryParamsSchema.shape,
+    pullNumber: z.number().positive(),
+  }).parse(params);
+
   const response = await githubRequest(
     `https://api.github.com/repos/${owner}/${repo}/pulls/${pullNumber}`
   );
@@ -93,20 +154,24 @@ export async function getPullRequest(
   return GitHubPullRequestSchema.parse(response);
 }
 
+/**
+ * Lists pull requests in a repository with optional filtering.
+ * 
+ * @param params Repository parameters and listing options
+ * @returns Promise resolving to an array of pull requests
+ * @throws {ZodError} If the input parameters fail validation
+ * @throws {Error} If the GitHub API request fails
+ */
 export async function listPullRequests(
-  owner: string,
-  repo: string,
-  options: {
-    state?: "open" | "closed" | "all";
-    head?: string;
-    base?: string;
-    sort?: "created" | "updated" | "popularity" | "long-running";
-    direction?: "asc" | "desc";
-    per_page?: number;
-    page?: number;
-  } = {}
-): Promise<z.infer<typeof GitHubPullRequestSchema>[]> {
+  params: RepositoryParams & Partial<ListPullRequestsOptions>
+): Promise<GitHubPullRequest[]> {
+  const { owner, repo, ...options } = z.object({
+    ...RepositoryParamsSchema.shape,
+    ...ListPullRequestsOptionsSchema.partial().shape,
+  }).parse(params);
+
   const url = new URL(`https://api.github.com/repos/${owner}/${repo}/pulls`);
+  
   Object.entries(options).forEach(([key, value]) => {
     if (value !== undefined) {
       url.searchParams.append(key, value.toString());