Codon Valuation

Estimate UK HMRC ordinary share value

estimate_emi_share_value

Read-onlyIdempotent

Gives an indicative range for the market value per ordinary share of a UK private company, as a planning estimate before agreeing an EMI valuation with HMRC (for example, to anticipate an EMI option exercise price). Uses the same methods as the 409A estimate, in pounds sterling: an option pricing model backsolve for a priced round in the last 12 months, otherwise a rolled-forward round, a sector revenue multiple, or an asset-based approach. Inputs are numbers from the shareholder register and accounts; no company or personal names are needed. Limitations: treats all preference shares as non-participating and pari passu, and does not model convertible instruments. The result is not an HMRC-agreed valuation.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "common_shares_outstanding": "<common_shares_outstanding>"
    },
    "name": "estimate_emi_share_value"
  }
}

Input Schema

Name	Required	Description
`cash`	No	Cash on hand, in pounds sterling.
`debt`	No	Interest-bearing debt, in pounds sterling.
`sector`	No	Company sector. Sets the default volatility and revenue multiple. Use 'other' if unsure.
`years_to_exit`	No	Expected years until a sale or IPO. Defaults to 3.
`volatility_pct`	No	Optional override for equity volatility, as a percentage.
`gross_margin_pct`	No	Gross margin, as a percentage.
`preferred_series`	No	Each priced preferred share round. Leave empty or omit if the company has never raised a priced round.
`revenue_growth_pct`	No	Year-over-year revenue growth, as a percentage (for example 40 for 40%).
`risk_free_rate_pct`	No	Optional current government bond yield matching years_to_exit, as a percentage.
`options_outstanding`	No	Number of share options granted and outstanding.
`revenue_last_12_months`	No	Revenue for the last 12 months, in pounds sterling.
`total_capital_invested`	No	Total equity capital invested to date, in pounds sterling. Used when there is no priced round and no revenue.
`common_shares_outstanding`	Yes	Number of ordinary shares issued and outstanding (excluding options and preferred).
`has_participating_preferred`	No	True if any preferred series is participating.
`performance_since_last_round`	No	How the company has performed against plan since its last priced round. Used when that round is more than 12 months old.
`has_unconverted_safes_or_notes`	No	True if the company has SAFEs or convertible notes that have not yet converted.
`options_weighted_average_strike`	No	Weighted average exercise price of outstanding options, in pounds sterling.

Schema Changelog

Changes observed during successful MCP inspections.

First observedOct 12, 2026

TDQS

A4.3/5.0

Behavior4/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), and the description adds real substance beyond them: the valuation method selection order (backsolve for a priced round within 12 months, else rolled-forward round, revenue multiple, or asset-based) and explicit modelling limitations on preference shares and convertibles. The only wobble is that it says all preferred are treated as non-participating and pari passu while the schema accepts has_participating_preferred and a per-series liquidation_preference_multiple, which an agent may find inconsistent.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Four sentences, front-loaded with what the tool produces before method, inputs, and caveats. Dense but each sentence carries distinct information; the methodology list is the only part that could be tightened for a caller who just needs the estimate.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a 17-parameter, read-only estimation tool with no output schema, the description covers purpose, method, input provenance, and limitations, and it characterises the return as an indicative range per share in GBP. It stops short of describing the shape of the result (e.g. a low/high range plus the method chosen), which would fully close the gap left by the absent output schema.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the baseline is 3 and the schema does the heavy lifting on the 17 fields. The description still earns a bump by telling the agent the inputs are register and accounts figures and that no company or personal names are needed, which shapes how the call is assembled rather than restating field definitions.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource with full scope: an indicative market value per ordinary share for a UK private company, in pounds sterling, for EMI planning. The UK/pounds framing and the explicit comparison to 'the 409A estimate' make it distinguishable from the sibling estimate_409a_value without opening either schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives a concrete when-to-use: before agreeing an EMI valuation with HMRC, e.g. to anticipate an option exercise price. It also sets a boundary by declaring the result is not an HMRC-agreed valuation, implicitly routing formal work elsewhere, but it never names get_formal_valuation_info as the alternative, so the exclusion is left to inference.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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