Summary Background Several workplace‐based formative assessment ( WFA ) tools exist; however, text‐based feedback is minimal but valuable because residents have difficulty extracting meaning from numerical scores or rankings. Our programme lacked a formal WFA programme, so we aimed to develop and assess a primarily text‐based tool, named formative assessment of skills in training ( FAST ), using action research. Methods Action research ( AR ) methods, including iterative plan–act–observe–reflect cycles that included the FAST tool and our clinical context. Thirteen residents and 11 faculty members performed 133 assessments during three study cycles, and responded to post‐use surveys. Results Overall, 83 per cent of participants indicated that FAST should be added to the resident curriculum. Time was perceived to be a barrier; however, time studies found that it did not prolong resident wait or patient visits. Changes were made to increase space for comments on the FAST form, and subsequently comment specificity and length increased. Discussion The FAST facilitates WFA in our programme and allows for specific written feedback with a copy retained by the resident. On average, it adds about 3 minutes to a clinic visit. The AR method facilitated WFA use, stakeholder buy‐in, and FAST tool improvements. The FAST facilitates WFA in our programme and allows for specific written feedback