{"uid":"cap_zy4IDEzmGL2BCMdMoTOc4","slug":"physics-constants-lookup-by-key-symbol-or-name-b412a2ff","name":"Physics Constants Lookup by Key, Symbol, or Name","description":"Look up a physical constant by its key (e.g. \"speed-of-light\"), symbol (e.g. \"c\") or exact name. Returns the CODATA 2018 recommended value, unit, relative standard uncertainty (0 for values that are exact by SI definition) and category.","url":"https://physics.openverbs.com/v1/constant","method":"POST","headers":{},"bodySchema":{"type":"object","$schema":"https://json-schema.org/draft/2020-12/schema","required":["input"],"properties":{"input":{"type":"object","required":["type","method","bodyType","body"],"properties":{"body":{"type":"object","required":["query"],"properties":{"query":{"type":"string","maxLength":60,"minLength":1,"description":"Constant key, symbol or exact name."}},"additionalProperties":false},"type":{"type":"string","const":"http"},"method":{"enum":["POST"],"type":"string"},"bodyType":{"enum":["json","form-data","text"],"type":"string"}},"additionalProperties":false}}},"responseSchema":null,"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"0.004","displayCostAsset":"USDC","priceDynamic":false,"priceHint":null,"priceStatus":"priced","priceSource":"probe","requiresHandshake":false,"reviewCount":0,"rating":{"score":"0.00","successRate":"0.00","reviews":0,"stars":null,"state":"unrated"},"availabilityStatus":"unknown","priceObserved":null,"sessionDeposit":null,"pricing":{"kind":"static","summary":"$0.004/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.004","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.004","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_VBwRv4SJmOXsJs_tmpU0H","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.004","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Looks up a single CODATA 2018 physical constant by its key, symbol, or exact name, returning its value, unit, uncertainty, and category.","exampleAgentPrompt":"What is the CODATA 2018 recommended value, unit, and uncertainty for Planck's constant? Look it up by its symbol 'h'.","exampleUseCases":[{"title":"Unit conversion calculation setup","prompt":"I'm writing a physics simulation and need the exact SI value and units of the speed of light — can you look it up by its key 'speed-of-light' and give me the CODATA 2018 recommended value?"},{"title":"Educational physics reference","prompt":"My student asked what the Boltzmann constant is — can you fetch its exact value, unit, and relative uncertainty from the CODATA 2018 dataset?"},{"title":"Engineering constants verification","prompt":"I need to double-check the gravitational constant G for a calculation — look it up by symbol 'G' and tell me its CODATA 2018 value, unit, and uncertainty."}],"resultDescription":"Returns the CODATA 2018 recommended value of the matched physical constant, along with its SI unit string, relative standard uncertainty (0 for exact SI-defined values), and a category label (e.g. universal, atomic, electromagnetic).","failureModes":["Query does not match any known constant key, symbol, or name — returns empty or not-found response","Ambiguous query matches multiple constants — may return best single match or an error","Input string exceeds 60 characters — rejected by schema validation","Payment not fulfilled via x402 protocol — request blocked before processing"],"whenToPreferThis":"Use this endpoint when you need an exact, authoritative lookup of a single physical constant by a known identifier (key, symbol, or full name) and want the CODATA 2018 recommended value with uncertainty. Prefer this over the search endpoint when you already know the identifier precisely and want a direct, deterministic result rather than a ranked list of candidates.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-09-14T18:41:23.319Z","isFirstParty":false}