What are ways to assess employability of workers? Employability is typically defined as 


  the continuous fulfilling, acquiring or
  creating of work through the optimal use of competences. (Van der Heijde &amp; Van der Heijden, 2006) 


One's employability does not only depend on one's ability to work (both physically and mentally), but also one's motivation to work and learn and the opportunity to work (Brouwers, 2012; dutch citation). 

Especially for elders, who are getting older and older, and have to work longer (i.e. until a higher age), employability is becoming incredibly relevant. They need to be able (and willing) to keep on working until their retirement, either in their current position or another less demanding job. This is a difficult job without clear insights. However, with such an incredibly broad term, it will even be difficult to gain those insights. 

Are there tools available to asses the personal factors of individuals' employability? 



Heijde, C. M., &amp; Van Der Heijden, B. I. (2006). A competence‐based and multidimensional operationalization and measurement of employability. Human resource management, 45(3), 449-476.

Brouwer, S., de Lange, A., van der Mei, S., Wessels, M., Koolhaas, W., Bültmann, U., ... &amp; van der Klink, J. (2012). Duurzame inzetbaarheid van de oudere werknemer: stand van zaken. Universitair Medisch Centrum Groningen, Groningen: Rijksuniversiteit Groningen.
Measures of person-job fit and/or person-organization fit. The following rather randomly assembled references are intended as links to some questionnaires. 

References

Chang, H.-T., Chi, N.-W., &amp; Chuang, A. (2010). Exploring the moderating roles of perceived person-Job fit and person-organisation fit on the relationship between training investment and knowledge workers’ turnover intentions. Applied Psychology: An International Review, 59(4), 566–593.

Kooij, D. T. A. M., van Woerkom, M., Wilkenloh, J., Dorenbosch, L., &amp; Denissen, J. J. A. (2017). Job crafting towards strengths and interests: The effects of a job crafting intervention on person–job fit and the role of age. Journal of Applied Psychology, 102(6), 971–981. https://doi.org/10.1037/apl0000194

Piasentin, K. A., &amp; Chapman, D. S. (2007). Perceived similarity and complementarity as predictors of subjective person-organization fit. Journal of Occupational and Organizational Psychology, 80(2), 341–354. https://doi.org/10.1348/096317906X115453

Saks, A. M., &amp; Ashforth, B. E. (1997). A longitudinal investigation of the relationships between job information sources, applicant perceptions of fit, and work outcomes. Personnel Psychology, 50(2), 395–426. https://doi.org/10.1111/j.1744-6570.1997.tb00913.x

Wheeler, A. R., Gallagher, V. C., Brouer, R. L., &amp; Sablynski, C. J. (2007). When person-organization (mis)fit and (dis)satisfaction lead to turnover: The moderating role of perceived job mobility. Journal of Managerial Psychology, 22(2), 203–219. https://doi.org/10.1108/02683940710726447