"error: ... An account required by the instruction is missing" when creating metaplex metadata account

Question

I've successfully implemented the minting function. After it, I added the method to create a metadata account. However, after I call the function, I get an error:

Error: failed to send transaction: Transaction simulation failed: Error processing Instruction 0: An account required by the instruction is missing
  at Connection.sendEncodedTransaction (node_modules/@solana/web3.js/src/connection.ts:4480:13)
  at processTicksAndRejections (internal/process/task_queues.js:95:5)
  at Connection.sendRawTransaction (node_modules/@solana/web3.js/src/connection.ts:4439:20)
  at sendAndConfirmRawTransaction (node_modules/@project-serum/anchor/src/provider.ts:284:21)
  at AnchorProvider.sendAndConfirm (node_modules/@project-serum/anchor/src/provider.ts:144:14)
  at MethodsBuilder.rpc [as _rpcFn] (node_modules/@project-serum/anchor/src/program/namespace/rpc.ts:29:16)

The method itself looks like this:

invoke(
        &token_instruction::create_metadata_accounts_v2(
            ctx.accounts.token_metadata_program.key(), 
            ctx.accounts.metadata.key(), 
            ctx.accounts.mint.key(), 
            ctx.accounts.authority.key(), 
            ctx.accounts.authority.key(), 
            ctx.accounts.authority.key(), 
            metadata_title, 
            metadata_symbol, 
            metadata_uri, 
            None,
            0,
            true, 
            false, 
            None, 
            None,
        ),
        &[
            ctx.accounts.token_metadata_program.to_account_info(),
            ctx.accounts.metadata.to_account_info(),
            ctx.accounts.token_program.to_account_info(),
            ctx.accounts.mint.to_account_info(),
            ctx.accounts.token_account.to_account_info(),
            ctx.accounts.authority.to_account_info(),
        ],
    )?;

And my struct is this:

#[derive(Accounts)]
pub struct MintToken<'info> {
    /// CHECK: We're about to create this with Metaplex
    #[account(mut)]
    pub metadata: UncheckedAccount<'info>,
    /// CHECK: This is the token that we want to mint
    #[account(mut)]
    pub mint: UncheckedAccount<'info>,
    pub token_program: Program<'info, Token>,
    /// CHECK: This is the token account that we want to mint tokens to
    #[account(mut)]
    pub token_account: UncheckedAccount<'info>,
    /// CHECK: the authority of the mint account
    #[account(mut)]
    pub authority: Signer<'info>,
    /// CHECK: Metaplex will check this
    pub token_metadata_program: UncheckedAccount<'info>,
}

I've checked everything back and forth, but couldn't find an account that I didn't fill out. The function that calls the program looks like this:

await program.methods.mintToken(
      nftTitle, nftSymbol, nftUri
    ).accounts({
      metadata: metadataAddress,
      mint: mintKey.publicKey,
      tokenProgram: TOKEN_PROGRAM_ID,
      tokenAccount: associatedTokenAccount,
      authority: key,
      tokenMetadataProgram: TOKEN_METADATA_PROGRAM_ID,
    })
    .rpc();

Can someone please help with why the error occurs?

Answer 1

I think you may need to include Rent for the metadata account:

#[derive(Accounts)]
pub struct MintToken<'info> {
    ...
    pub rent: Sysvar<'info, Rent>,
}

Then just add:

ctx.accounts.rent.to_account_info(),