Deep structured analysis of one project by slug: what it is, entry, signature needs, risks, verdict.

Compute (base ^ exponent) mod modulus efficiently for arbitrary-precision integers. The modulus must be positive.

Euler's totient φ(n) — the count of integers in [1, n] coprime to n — for a positive integer ≤ 10^15 (it is computed from the prime factorization).

Generate an RFC 4226 counter-based HMAC one-time password from a base32 secret and counter. Configurable digits (6–10, default 6) and algorithm (SHA1/SHA256/SHA512, default SHA1). An invalid base32 secret is a clean 400.

Multifamily development underwriting — construction to hold to exit. Models construction draws (S-curve or straight-line), capitalized interest, lease-up ramp, construction-to-perm refi, and hold period returns. Returns development yield on cost, spread to cap rate, profit on cost, IRR and MOIC.

Industrial acquisition underwriting — NNN and gross lease multi-tenant. Per-tenant lease modeling with contractual rent bumps and rollover vacancy. Blended OpEx based on NNN vs gross SF mix. Returns cap rate, NOI per SF, WALE, DSCR, IRR and MOIC.

Single-Family Rental (SFR) underwriting — monthly buy-and-hold proforma to unlevered AND levered project returns (IRR via XIRR + equity multiple). Loan-to-cost financing, optional interest-only, appreciation-floored exit. Deterministic, Excel-reconciled, SHA-pinned (pass attest=true).

Search the constants table by key, symbol or name substring. Exact matches rank first, then prefix matches, then substring matches. Returns up to `limit` constants (default 20) plus the total match count.

Multifamily acquisition underwriting — mixed unit mix through a monthly proforma to unlevered AND levered project returns (IRR via XIRR + equity multiple). Stub acquisition month, trailing-NOI exit. Deterministic, Excel-reconciled, SHA-pinned (pass attest=true).

Generate an RFC 6238 time-based one-time password from a base32 secret. Uses the current time by default, or an explicit unix timestamp (seconds); configurable period (default 30s), digits (default 6) and algorithm (default SHA1). Also returns the counter and seconds remaining in the window.

Render a barcode (Code128, Code39, EAN-13/8, UPC-A/E, ITF-14, DataMatrix, PDF417) as SVG or PNG data URL.

Evaluate one or more percentiles (0–100) of a numeric sample using linear interpolation between order statistics (the R-7 / Excel PERCENTILE.INC method). 50 is the median, 25/75 the quartiles.

Verify a submitted TOTP code against a base32 secret, scanning ±window time steps (default ±1) to tolerate clock drift. Returns valid plus the matching step offset (delta). A code that does not match is a successful result with valid=false — not an error.

Expand a fraction to its decimal form by exact long division, detecting a repeating cycle and rendering it in parenthesis notation (e.g. 1/6 → '0.1(6)', 1/7 → '0.(142857)'). maxDigits caps a non-repeating expansion. A zero denominator is a clean 400.

Build braille cells from raised-dot numbers (each cell an array of 1–8). Out-of-range or repeated dots are clean 400s.

CRC-32 (IEEE 802.3 polynomial, as used by zip, gzip and PNG) over the input payload. Returns the checksum as an unsigned integer and 8-digit hex. Non-cryptographic — for error detection only.

Rebuild a nested object from a single-level object whose keys are delimited paths (default delimiter `.`) — the inverse of flatten. Requires a flat object.

Infer a JSON Schema (draft-07) from a sample document in any supported format. Types are inferred, present keys are marked required, and heterogeneous array item schemas are merged. The result validates out of the box with /v1/validate.

Parse a document (json, json5, jsonc, yaml, xml, csv, tsv, toml, ndjson, ini, env, properties, plist or querystring) and validate it against a JSON Schema. Returns whether it is valid and a list of precise, path-tagged errors. Malformed input or an invalid schema is rejected before payment.

Compute a cryptographic digest (SHA-2, SHA-3, BLAKE2, and legacy SHA-1/MD5/RIPEMD-160) of some data. The input may be utf8/hex/base64/base64url and the digest is returned as hex/base64/base64url.