A certificate of insurance (COI) is proof that a policy exists on the date the certificate was issued. It is not the policy itself, and issuing one to a customer does not modify coverage.
The standard form is the ACORD 25. Read it from top to bottom: producer (your agent), insured (you), insurers affording coverage (each with an A.M. Best rating), and then the coverages grid.
Verify each policy: type, policy number, effective and expiration dates, and limits. The limits column is where fraud hides — inflated numbers on a certificate that don't match the actual policy.
The 'Description of Operations' box is where additional-insured and waiver-of-subrogation wording lives. Never accept generic 'as required by written contract' language without confirming the underlying endorsement is actually on the policy.
Ask for an ACORD 855 for Washington public works or a Form E for trucking authority — different jobs use different forms.