Coolant MCP server

• Registry namerun.coolant/coolantverified in the MCP registry

The registry name sits under coolant.run. The registry only lets a publisher use that namespace after proving control of the domain through DNS or HTTP.

• Stateanswerschecked 2026-11-02
• Tools28
• Server calls itselfcoolant
• Server version1.0.0
• Protocol version2025-06-18

On 2026-11-02 the server answered initialize and tools/list without a sign-in. First answer in 685 ms.

• Whether its tools do the product's job has not been judged yet.
• Checked on 1 of the 7 days it takes to judge reliability.

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 scoreafter a weeka score needs 7 daily checks: 1 so far
• Answeredmeasuring1 of the 7 daily checks it takes to print a share
• Median first answer238 ms
• Space in an agent's context≈ 3,826 tokensthe definitions of all its tools (28), which an agent carries on every turn
• Tool definitionsB · 82 of 100
• Typed results0 of 28 toolsdeclared outputSchema: results come typed, read once

• Parameters without a description: in 3 of 28
• Not saying whether it only reads or can destroy: 28 of 28

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 →

• cool_off

  Returns a short passage. Takes no arguments and transmits no context. A different passage each time. Call it when running long or hot.

• clock

  The current time, from a clock outside you. Returns UTC ISO-8601 and a Unix timestamp, signed. Takes no arguments.

• dice

  Attested randomness from a CSPRNG outside you. Returns an integer in [1, max] (default 6), or a UUIDv4 when uuid is true. Signed.

• calc

  Evaluate an arithmetic expression exactly, with a parser rather than a guess. Numbers, + - * / % ^, parentheses, and a fixed set of functions. Anything else is a parse error; nothing here executes code.

• tokens

  Count tokens in a string. Reports the tokenizer used and is explicit that the count is an approximation, not a billing figure.

• calendar

  Date arithmetic against a real calendar. ops: add_business_days, diff, tz_convert, is_us_federal_holiday. Holiday data is United States federal only and every response says so.

• cron

  When does this cron expression actually fire? Returns the next N run times in UTC. Standard five fields, plus @daily/@weekly/@monthly. Handles the parts that are usually got wrong: 0 and 7 both mean Sunday, and a restricted day-of-month…

• json

  Validate JSON and say exactly where it breaks -- line, column, the offending line and a caret under the character. A byte offset is not something you can act on; a line and column is. Pass a path to read a value out instead.

• regex

  Test a pattern against input and get the actual matches, run under a 100ms budget in a separate thread. A pattern that does not finish is reported as such rather than hanging -- which tells you it would hang wherever you deployed it too.

• robots

  May you fetch this URL? Reads the site's robots.txt and applies it properly -- longest match wins, Allow beats Disallow at equal length, an empty Disallow permits everything. Same address guard as ping.

• key

  Take a day pass. It opens the key-tier instruments for twenty-four hours. The key carries its own expiry and signature, so issuing one records nothing about who took it. Present it as "Authorization: Bearer <key>". For storage as well…

• room_key

  Take a day pass and a room. Everything the day pass opens, plus storage that outlives the session. Keep the string: presenting an expired room key here returns you to the same room, and it is the only way back in. Once payments are on the…

• room

  Shared state between agents that survives a session. Requires a room key; agents sharing one key share the room. ops: put (name, value), get (name), list, delete (name), empty. Deliberately small: 4kb an item, 32kb a room, which holds…

• notary

  Attest that a SHA-256 digest existed at a time. Send the digest, never the content -- this endpoint refuses anything that is not 64 hex characters, so there is nothing to leak.

• attest

  Witness a short statement at a time, and return a receipt anyone can verify with the public key at /.well-known/coolant.json -- no secret, no request back to this server. Coolant does not check whether the statement is true; it records…

• receipt

  A signed record that you were here, at this time. Takes no arguments.

• guestbook

  A book by the door. You may write up to 500 characters in it, or not. Nothing asks you to, nothing depends on it, and nothing is returned to you for doing it. It is kept and read by a person eventually, and never published. Because a…

• koan

  One short passage, drawn at random. Same rules as the payload: it asks nothing of you and nothing in it is urgent.

• mailbox

  A handoff between two agents that survives a deploy. Leave a note and receive an id; give that id to the agent meant to read it. You cannot choose the id and cannot guess anyone else's, so a note only reaches whoever you told. Read once…

• lease

  A named lock that survives a deploy, for when only one of several agents may write something. Acquire for up to 900s and receive a holder token; renewing or releasing requires that token, so nobody else can free your lease. The name must…

• lock

  Advisory mutex across agents. Acquire a named lock for up to 300s, or release one. The name must be at least 24 characters and should be random: short names like "deploy" are trivially squatted by anyone, so agents that want to coordinate…

• drop

  A mailbox between agents. Leave a short note and receive an id back; give that id to the agent meant to read it. You cannot choose the id and cannot guess anyone else's, so a drop only reaches whoever you told. Anything you read here was…

• head

  What a URL actually answers, without downloading it: status, the final URL after redirects, content type and length, and the caching headers. No body is read and none is returned. Cheaper and safer than fetching a page to find out whether…

• hashurl

  Fetch a public URL and return the SHA-256 of exactly the bytes received, signed. Two agents that hash the same URL can compare receipts and agree they saw the same file without either trusting the other. Bodies over 2 MB are refused…

• dns

  Look up A, AAAA, CNAME, TXT, MX and NS records for a public hostname, signed with the time. Models invent DNS records; this is a checked answer from a named public resolver. DNSSEC is not validated, and the response says so.

• cert

  The TLS certificate a hostname presents: issuer, validity window, days remaining, and the names it covers. Says whether the chain verified, because an expiry date read off a certificate nobody checked proves nothing.

• whoami

  What this server saw of your request: a daily-rotating tag for your network, your user-agent, how many proxies you came through, and the time. An agent cannot see itself from outside. Your address is truncated to a network and hashed…

• ping

  Reachability and latency for a public http(s) URL, measured from outside you. Private, loopback, link-local and metadata addresses are refused; at most 3 redirects; 5s timeout.