cost-benefit

What it does

Produces a Green Book-style economic case (NPV, BCR, optimism bias, sensitivity) alongside a parallel financial case (cash flow to the sponsor, Financial NPV, payback, DSCR if debt is involved), with a one-line headline verdict telling you whether the project is socially worthwhile and financially self-sustaining.

How it works

• Detects computation backend by probing the greenbook bridge; if available, uses econstack-greenbook with action appraise and reads NPV, BCR, OB-adjusted streams, METB, discount factors from JSON; otherwise computes internally using defined formulas and notes a fallback footnote.
• Step 1 loads project, options, costs, and benefits either from a --from longlist markdown file (parsing project name, framework, sponsor, benefits and costs tables) or by prompting the user in one AskUserQuestion batch for project description, options (including Do nothing), costs (capital and Opex), and benefits (annual benefit and type).
• Step 2 computes the results silently, presenting outputs in the final markdown. When using the greenbook backend, prefers the bridge for NPV/BCR/discounts; otherwise uses inline calculations described in the skill.
• Real-terms rebasing (uk-gb) applies gb_rebase to inputs if needed; discount factors depend on the backend: greenbook provides them, otherwise a kinked STPR-based computation for uk-gb.
• Includes capital cost phasing (S-curve) for multi-year construction, optimism bias adjustments with mitigation, and METB application for tax-financed costs under uk-gb.

When to use it

Used when a project needs a structured cost-benefit appraisal with both economic and financial perspectives, cross-framework support, and potential use of a longlist file as input.

What it can touch

• Reads files from a longlist markdown via --from. The safety rules state the parameter database is read-only and cannot be written to.
• Interacts with the econstack-greenbook bridge if available. Commands and actions include actions like "version" and "appraise", accessed through the bridge executable. The exact commands and script names are quoted and executed as described in the skill.

Caveats

• Backend choice depends on the availability of the greenbook bridge; if unavailable, calculations fall back to internal methods with a note about missing greenbook reproducibility.
• The preamble includes explicit guidance on how to handle parameter and learnings data locally; no data is transmitted externally.
• The skill requires one of several frameworks (uk-gb, eu-brg, wb, adb, au-vic) and uses the corresponding discount rates and welfare weights as defined in the supported frameworks section.