0s and 1s CIS Filing MCP server

• Registry nameuk.co.0sand1s/cisverified in the MCP registry

The registry name sits under 0sand1s.co.uk. The registry only lets a publisher use that namespace after proving control of the domain through DNS or HTTP.

• Stateanswerschecked 2026-10-27
• Tools7
• Server calls itself0s and 1s
• Server version1.0.1
• Protocol version2025-06-18

On 2026-10-27 the server answered initialize and tools/list without a sign-in. First answer in 211 ms.

• Whether its tools do the product's job has not been judged yet.

Said by rules from the measurements above. The likely first call is a model's pick from the tool list; read its description before relying on it.

• INITE MCP score87 of 100answers 100 · definitions 100 · context 100 · use 0 · connects 100
• Answered100% of days7 of 7 daily checks
• Median first answer905 ms
• Space in an agent's context≈ 2,251 tokensthe definitions of all its tools (7), which an agent carries on every turn
• Tool definitionsA · 100 of 100
• Typed results0 of 7 toolsdeclared outputSchema: results come typed, read once

• Every tool passes all six checks.

A program checks the server once a day: initialize and tools/list, no model. Tokens are the definitions' length at about four characters a token. The grade averages six checks of every tool's name, description, schema and annotations; it says how well the tools are described, not whether they work. The score weighs what was measured and nothing else: answering (25%), doing the product's job (25%), definitions (20%), context (10%), use (10%) and how readily a client connects (10%). A part that was not measured is left out, and a hidden instruction caps the score at 40. The state of vendors' MCP servers: method and numbers →

• cis_deduction

  Works out the CIS deduction on a payment to a subcontractor, from the gross bill to the net payment. Takes the gross including VAT, the VAT, the subcontractor's materials and the rate (0, 20 or 30). VAT is never taxed under CIS and…

• cis_gross_up

  Finds the gross amount (excluding VAT) that leaves a given net payment after the CIS deduction, for a subcontractor quoted a take-home figure. Takes the net, the subcontractor's materials and the rate (0, 20 or 30). Where rounding lets…

• cis_tax_month

  For a date, gives the CIS tax month it falls in (the 6th to the 5th), the tax year, the date the monthly return (CIS300) is due (the 19th, also the date for paying HMRC by any means other than electronically), and the date for paying HMRC…

• cis_late_penalties

  Works out the late filing penalties on one monthly CIS return under Finance Act 2009 Schedule 55: £100 the day after the 19th, £200 at 2 months, then the greater of £300 and 5% of the deductions at 6 and at 12 months (5% alone for a first…

• cis_gross_payment_turnover_test

  Checks the turnover test for CIS gross payment status (Finance Act 2004 Schedule 11, SI 2005/2045 reg 28): £30,000 net construction turnover for a sole trader; for a partnership or company, the lower of £30,000 for each partner or…

• cis_needs_verification

  Says whether a contractor must verify a subcontractor with HMRC before paying them (SI 2005/2045 reg 6): not needed if the subcontractor was on one of this contractor's CIS returns, or was verified by this contractor, in the tax year of…

• cis_nil_return_check

  Says whether a contractor must file a CIS nil return for a tax month (SI 2005/2045 reg 4(9A) and (9B), inserted by SI 2026/289 from 6 April 2026): due when a mainstream contractor that has paid subcontractors before pays none that month…