Nine tool definitions reach every capability: the catalogue is a SQL table, not a prompt

Evidence status

Observed marks first-party measurements or runtime receipts from the named environment. Derived marks arithmetic calculated from cited inputs. Specified marks vendor or standards documentation. Implemented and deployed name code and live-state evidence, respectively. Reproduced means the stated procedure was rerun. Externally attested marks operator reports; those reports show that an experience occurred, not that it is universal.

The same catalogue, exposed three ways, measured on the same day

One build, one table, one model. Only the exposure changes. Measured 2026-07-25 on @cf/moonshotai/kimi-k2.7-code through Cloudflare AI Gateway, claude-cli 2.1.165 as the client, figures read from gateway log rows and wire captures rather than estimated.

All three rows reach the same capabilities. The first costs 10.6× the input tokens of the third for identical reach.

The honest finding: at this size the two cheap designs cost the same

14,109 against 14,071 is a difference of 38 input tokens, 0.27%. In dollars the deferred-tool turn came out 3.0% cheaper, because the turn totals include output tokens and the two turns did not produce identical output. Anyone reading this page for a cost argument between rows two and three will not find one. At 891 rows, deferred tool search and catalogue-as-data are the same price.

The difference is structural, and it does not expire when the numbers do:

• Row two's cost is a function of how many definitions the model retrieves. Row three's is a function of the protocol, which is four endpoints regardless of table size.
• Row two needs the host to implement deferral. Row three needs the model to be able to make an HTTP request.

What would falsify the structural claim: a harness where deferred loading is free at any catalogue size and is implemented uniformly across clients. Section "Deferral is a host feature, and hosts disagree about it" is where that claim currently breaks. What would falsify the cost claim: a catalogue an order of magnitude larger, where the retrieved-definition cost of row two starts to bite while row three stays flat. That measurement has not been taken here and is not claimed.

defer_loading controls context, not the request

The vendor documentation is explicit about what deferral does and does not remove, and it is the single most load-bearing fact on this page:

defer_loading controls what enters the context window, not what you send in the request: You still send every tool's full definition in the tools array on every request, including the deferred ones. The API needs them server-side to run the search and expand tool_reference blocks.

— Anthropic, Tool search tool

So the catalogue is still enumerated, still serialised, still transmitted, every turn. It is simply not billed as context. On this build that array would be 831 tool objects and 451,197 bytes of JSON, measured live below. The client is doing that work whether or not the model reads it.

Anthropic also publishes the billing rule that makes definitions expensive in the first place: pricing counts "the total number of input tokens sent to the model (including in the tools parameter)". Names, descriptions and schemas are input tokens. They are re-sent every turn. They scale with how many capabilities exist.

Two independent numbers put a floor under that. Anthropic's own doc says a five-server setup — GitHub, Slack, Sentry, Grafana, Splunk — "can consume ~55k tokens in definitions before Claude does any work". The Scalekit benchmark, 5 GitHub tasks against anthropics/anthropic-sdk-python, Claude Sonnet 4, pre-registered hypotheses and 30 runs per arm, found the simplest task cost 1,365 tokens through a shell and 44,026 through GitHub's MCP server, and attributes it: "The difference is almost entirely schema: 43 tool definitions injected into every conversation, of which the agent uses one or two."

Divide this build's own numbers the same way. (149,187 − 14,071) ÷ 856 = 157.8 input tokens per definition. That is close to the back-of-envelope a commenter used on Hacker News — "Say each tool is 150 tokens, that's 150 * 50, or 7500 tokens, dumped into the beginning of every session" — which means the per-definition constant is stable enough to plan against.

One row is one capability, and this is one row

AIG_LIST lists the AI Gateways on a Cloudflare account. Read live with:

curl -s "https://miscsubjects.com/api/directory/AIG_LIST" -H "x-terminal-key: $TERMINAL_KEY"

Every field it carries, verbatim:

The field list is not folklore — it is declared in code at /Users/cyrusmassoumi/miscsubjects-pages/functions/_lib/dir_schema.js lines 6–29, which is embedded in /api/directory responses so a client can learn the shape without prior knowledge. The docstring parser that splits # lines from the payload is extractDocs/stripDocs in functions/api/dispatch.js lines 431–450.

The full field reference, all four type values and what each runner does: What a directory row is.

Four counts of the same catalogue, all of them correct

Ask the build how many capabilities it has and you get four different numbers. They are not a bug and they must not be reconciled by editing one to match another. Each is a different predicate over the same table.

Taken live at 2026-07-26T04:37:42Z:

npx wrangler d1 execute loop-content-spine --remote --command \
  "SELECT COUNT(*) AS rows_total,
          SUM(CASE WHEN IFNULL(enabled,1)=1 THEN 1 ELSE 0 END) AS enabled,
          SUM(CASE WHEN IFNULL(enabled,1)=1 AND IFNULL(planner_visible,1)=1 THEN 1 ELSE 0 END) AS mcp_projected
   FROM directory;" --json

The measurement day's figures were 891 / 878 / — / 856. The table is live and other writers touch it, so a rerun returns whatever it holds at that instant; between the first and last command in this session a row was inserted by another process. That is the point of the design, not an inconvenience to it. The gap between 892 and 832 — 60 rows — is entirely disabled rows plus rows deliberately hidden from planners.

Counting the projection, live

The MCP projection is a real server and the definition array can be weighed directly. Command:

curl -s -X POST https://miscsubjects.com/api/mcp \
  -H "Authorization: Bearer $MCP_TOKEN" \
  -H 'content-type: application/json' \
  -H 'accept: application/json, text/event-stream' \
  -d '{"jsonrpc":"2.0","id":1,"method":"tools/list"}'

Result at 2026-07-26T04:38Z: 831 tools, 451,197 bytes of tools array, mean 543 bytes per definition. That is the payload a client sends on every request under defer_loading, and the payload a model reads without it.

A model that has never seen this build gets from question to receipt in four calls

No SDK, no client library, no prior knowledge. Four HTTP calls.

1 — Ask in plain language. GET https://miscsubjects.com/api/dispatch?ask=what%20time%20is%20it returns count: 12, a best block, and twelve ranked candidates each with a runnable URL:

"best": { "key": "NOW",
          "run_now": "https://miscsubjects.com/api/dispatch?invoke=NOW&share=<TOKEN>",
          "do": "Open run_now to do it. Substitute your own text/args where the example has them." }

2 — Read the contract. GET https://miscsubjects.com/api/dispatch?key=NOW&format=markdown returns that capability's _self block: what it is, the exact POST shape, the argument template, the output contract, the auth and risk level, the troubleshooting table, and the ledger and repair addresses.

3 — Invoke. POST https://miscsubjects.com/api/dispatch {"key":"NOW","body":""}.

4 — Take the receipt. The response carries proof.invocation_id and three addresses: a credentialed forensic receipt, a keyless public confirmation, and a public brochure.

Each step with its full request and response: The four-step loop.

The resolver is a substring scorer, and the tail of its output is noise

answerAsk at functions/_lib/object_contract.js:605-640 scores every enabled row: +3 if a query term appears in the key, +1 if it appears anywhere in key, category or docstring, +1000 for a hand-pinned canonical match, −6 for a row on the demote list. Top twelve are returned.

For ?ask=what is it the pinned answer is right and the rest is garbage. The live twelve for "what time is it":

NOW, GITHUB_LIST_ISSUES, GITHUB_GET_ISSUE, GITHUB_ADD_ISSUE_COMMENT, GITHUB_CREATE_ISSUE, GITHUB_CLOSE_ISSUE, LOCAL_EDIT, LOCAL_WRITE, CLI_GIT, WRITER_AGENT, BLOOIO_LIST_CONTACT_IDENTITIES, STRIPE_INVOICE_ITEMS_LIST

The GitHub rows match because the two-character term is is a substring of issue. There are no embeddings, no BM25, no stemming and no synonym table. A query using a word the row never uses will miss it. Anthropic's own tool search offers BM25 and regex variants for exactly this reason, and one commenter names the trade honestly: "Seems like we traded scalability for accuracy, then accuracy for scalability… but I guess maybe we've come out on top because whatever they are using for tool search is better than RAG?" On this build the mitigation is the recommended pin, which is a hand-maintained list, which is a real maintenance cost.

What a row carries that a list of endpoints does not

"Put it behind an API" is not the same design. Five things live in the row that a bare endpoint list leaves to convention:

The strongest objection to all of this, from someone who means it

The case against is not "MCP is fine". It is that a decorated index of features beats a bare endpoint list for a model, and that decoration is the whole product:

It's like saying APIs are dead because you can just use HTTP. They're not the same thing, though of course you can hand-roll the higher layer in the lower one. It's just more work, less standard, less valuable.

— brookst, Hacker News, 2026-05-30

That is correct as stated, and this design does not contradict it. The directory row is the decorated index: the decoration is the docstring, the auth field, the schema and the flags. What is rejected is the claim that the decoration must arrive as tool definitions in the prompt. A second commenter puts the same point at the protocol level — "The idea that MCP tool definitions take up a certain number of tokens is laughable. That's an implementation detail of the agent harness." — and a third calls deferral table stakes: "Most mature harnesses do some kind of tool search and/or progressive disclosure."

Both are right that token cost is a harness property. The reply is narrow: a harness property is exactly the thing this design refuses to depend on.

Deferral is a host feature, and hosts disagree about it

That refusal is not theoretical. Every claim below is a filed, reproducible report:

The last two matter for the next section: the MCP specification's answer to adding a capability at runtime is that servers "SHOULD send a notification", notifications/tools/list_changed. It is a SHOULD on the server and a silent no-op in at least two shipping clients.

The 892nd capability costs one POST and no deploy

Not an argument — a round trip run for this page.

curl -X POST https://miscsubjects.com/api/directory \
  -H "x-terminal-key: $TERMINAL_KEY" -H 'content-type: application/json' \
  -d '{"key":"__DOC_PROBE","type":"http",
       "target":"GET https://miscsubjects.com/api/dispatch?key=TIME_NOW",
       "category":"docs","content":"# WHAT: Probe row created to time one capability insert.\n# ARGS: none\n"}'

Response, HTTP 201 in 0.437946 s:

{"ok":true,"key":"__DOC_PROBE","updated_at":"2026-07-26T04:36:08.555Z"}

Row count went 891 → 892. No build, no deploy, no client restart, no reconnect. Thirty-five seconds later — the directory snapshot cache is a 30-second KV entry, set in loadDirectory() at functions/api/dispatch.js:413-429 — the new capability had a full self-describing contract at ?key=__DOC_PROBE, and invoking it returned:

{"ok":true,"ran":true,"proof":{"ok":true,"did":"DONE — __DOC_PROBE",
 "invocation_id":"inv_z77vqe1qi6",
 "public_receipt":"https://miscsubjects.com/receipt/inv_z77vqe1qi6"}}

The receipt is still public: GET https://miscsubjects.com/api/dispatch?confirm=inv_z77vqe1qi6 returns "confirmed": true with no credential. The probe row was then deleted (DELETE /api/directory/__DOC_PROBE → {"ok":true,"deleted":1}); the receipt survives the row, because receipts are append-only and rows are not.

The equivalent under definitions-in-context is: publish a new definition, emit notifications/tools/list_changed, and hope the client re-queries. Two of the clients above do not.

Where this design loses

Stated plainly, because a page that argues one way is not worth reading.

• It needs a running service. The catalogue is a table behind a Worker. If miscsubjects.com is down, there are zero capabilities. An MCP server on stdio keeps working with no network.
• There is no client-side discovery. Nothing enumerates the catalogue into a UI, a permission prompt or a tool picker. MCP clients render tool lists, ask for consent per call, and show the user what the model can reach. The specification says implementations "SHOULD" keep a human in the loop; here the human-in-the-loop surface has to be built.
• A model that cannot make HTTP calls cannot use any of it. Every model behind this page can. That is an assumption, not a law.
• There is no ecosystem. No marketplace, no registry of third-party servers, no npx one-liner, no standard anyone else implements. Wrapping someone else's MCP server means writing rows.
• Retrieval quality is worse than a purpose-built search. Substring scoring plus a hand-pinned list, versus BM25 or regex with a vendor tuning it.
• The resolver is a single point of failure for discovery. If ?ask= ranks wrong, the model does not know what it missed. A full definition list has no ranking to get wrong.
• Round trips. Discovery is a network call before the work. One commenter frames the whole MCP-versus-in-context debate this way — "I call this 'speed of light' as opposed to 'carrier pigeon'" — and the criticism lands here too: reading a contract costs a turn that an in-context definition does not.

The month, multiplied out

At 200 model turns per day, one seat, the measured per-turn costs above:

$171.13 − $27.38 = $143.75 a month per seat, for exactly the same reach. Between the two cheap rows the difference is $0.79 a month, which is not a reason to choose either. Choose row three when the capability layer has to outlive one vendor's tool-calling implementation; choose row two when the host already implements deferral and the catalogue is already MCP servers.

The full dimension-by-dimension comparison: Tool Search and catalogue-as-data, compared. What the per-row MCP projection is for and when to attach it: MCP as a projection, not a home.

Symptom, cause, fix