api-linter

api-linter is a skill for Claude Code from cyanheads/obsidian-mcp-server. It costs 86 tokens per session (12,812 once invoked), scanned A, original, Apache-2.0.

A reference for the rules used by an MCP definition linter. MCP is a standard way for AI applications to expose tools, data sources, and prompts; a linter checks their definitions before they are used.

In plain words
What is it for?
Use it when `bun run lint:mcp` or `bun run devcheck` reports issues such as invalid schemas, naming problems, or mismatched server configuration.
Why use it?
It explains what each reported rule means, whether it is an error or warning, and how to correct it. This makes build or pre-commit failures easier to diagnose.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin. Also seen: mentions CLAUDE.md; mentions Claude Code; mentions AGENTS.md.

Part of the obsidian-mcp-server plugin — 32 skills, 1 MCP server shipped together

Good fit Use it when bun run lint:mcp or bun run devcheck reports issues such as invalid schemas, naming problems, or mismatched server configuration.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/cyanheads/obsidian-mcp-server/api-linter
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add cyanheads/obsidian-mcp-server --skill api-linter
Clone the repo
git clone --depth 1 https://github.com/cyanheads/obsidian-mcp-server

Made for: Claude Code.

Or install obsidian-mcp-server, the plugin that ships this one along with the rest of its 32 skills, 1 MCP server.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for api-linter

README.md
[![agentmods](https://agentmods.dev/badge/skills/cyanheads/obsidian-mcp-server/api-linter/github.svg)](https://agentmods.dev/skills/cyanheads/obsidian-mcp-server/api-linter)
Your own site
<a href="https://agentmods.dev/skills/cyanheads/obsidian-mcp-server/api-linter"><img src="https://agentmods.dev/badge/skills/cyanheads/obsidian-mcp-server/api-linter/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for api-linter

Your own site · 80×15
<a href="https://agentmods.dev/skills/cyanheads/obsidian-mcp-server/api-linter"><img src="https://agentmods.dev/badge/skills/cyanheads/obsidian-mcp-server/api-linter.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 86 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 12,812 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector warn 7 Sept 2026
SkillSpector: 5 findings, up to medium

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

  • medium Excessive Agency · line 130
    Skill enables autonomous high-impact decisions without human-in-the-loop verification. Critical operations (destructive commands, financial transactions, data deletion) should require explicit user confirmation.
    Fix: Add human-in-the-loop confirmation for destructive, irreversible, or high-impact operations. Never auto-execute commands that modify files, send data, or alter system state.
  • medium Agent Snooping · line 21
    Skill enumerates or reads other installed skills. Access to other skills' SKILL.md files or the skills directory reveals prompt instructions, capabilities, and secrets that should be invisible to peer skills.
    Fix: Remove all code or instructions that list or read other skills' files or directories. Skills should operate independently; cross-skill access is a privilege escalation.
  • medium Agent Snooping · line 618
    Skill enumerates or reads other installed skills. Access to other skills' SKILL.md files or the skills directory reveals prompt instructions, capabilities, and secrets that should be invisible to peer skills.
    Fix: Remove all code or instructions that list or read other skills' files or directories. Skills should operate independently; cross-skill access is a privilege escalation.
  • medium Agent Snooping · line 695
    Skill enumerates or reads other installed skills. Access to other skills' SKILL.md files or the skills directory reveals prompt instructions, capabilities, and secrets that should be invisible to peer skills.
    Fix: Remove all code or instructions that list or read other skills' files or directories. Skills should operate independently; cross-skill access is a privilege escalation.
  • medium Output Handling · line 901
    Output size or generation rate is not bounded. Unbounded output enables denial-of-service through resource exhaustion, log flooding, or context-window stuffing.
    Fix: Set explicit limits on output length, generation count, and rate. Use max_tokens and truncation to prevent unbounded output.
How audits are shown
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00086 $0.12812
Opus 5 $0.00043 $0.06406
Sonnet 5 $0.00017 $0.02562
Haiku 4.5 $0.00009 $0.01281

Measured 3d ago against content hash cf57d7e35c3a, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-08, from the pricing page.

Security

Grade A, and why

api-linter scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 3d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Origin

Copies of this mod

8 near-identical copies found in the catalogue:

skills/api-linter/SKILL.md · 984 lines

How it starts

The opening of the file, as written. The whole thing — 984 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Overview

The linter validates tool, resource, and prompt definitions against the MCP spec and framework conventions. It is build-time only — not invoked at server startup. It runs in two places:

Entry point When On failure
bun run lint:mcp Manual or CI Prints errors + warnings, exits non-zero on errors.
bun run devcheck Pre-commit workflow Wraps lint:mcp alongside typecheck, format, bun audit, bun outdated.

Both surface the same LintReport from validateDefinitions() (exported from @cyanheads/mcp-ts-core/linter). Each diagnostic has a stable rule ID — that's the anchor you land on via the See: skills/api-linter/SKILL.md#<rule> breadcrumb appended to every message.

Severity:

  • error — MUST-level spec violation; blocks devcheck.
  • warning — SHOULD-level or quality issue; logged but devcheck continues.

Imports (if you need to run the linter programmatically):

import { validateDefinitions } from '@cyanheads/mcp-ts-core/linter';
import type { LintReport, LintDiagnostic } from '@cyanheads/mcp-ts-core/linter';

const report = validateDefinitions({ tools, resources, prompts, serverJson, packageJson });
if (!report.passed) process.exit(1);

Rule index

Grouped by family. Jump to any rule ID via its anchor.

Family Rules Section
Definition definition-invalid Definition rules
Format parity format-parity, format-parity-threw, format-parity-walk-failed, format-parity-depth-limit Format parity
Schema schema-is-object, describe-on-fields, schema-serializable, schema-unsatisfiable, header-param-designation Schema rules
Portability schema-format-portability, schema-anyof-needs-type, schema-no-discriminator-keyword, schema-no-defs, schema-root-oneof-portability, schema-dialect-tag Portability rules
Names name-required, name-format, name-unique Name rules
Tools description-required, handler-required, auth-type, auth-scope-format, annotation-type, annotation-coherence, meta-ui-type, meta-ui-resource-uri-required, meta-ui-resource-uri-scheme, app-tool-resource-pairing, canvas-consumer-missing Tool rules
Resources uri-template-required, uri-template-valid, resource-name-not-uri, template-params-align Resource rules
Landing landing-* (23 rules — shape, tagline, logo, links, repo, envExample, connectSnippets, theme) Landing config rules
Prompts generate-required Prompt rules
Handler body prefer-mcp-error-in-handler, prefer-error-factory, preserve-cause-on-rethrow, no-stringify-upstream-error Handler body rules
Error contract (structural) error-contract-type, error-contract-empty, error-contract-entry-type, error-contract-code-type, error-contract-code-unknown, error-contract-code-unknown-error, error-contract-reason-required, error-contract-reason-format, error-contract-reason-unique, error-contract-when-required, error-contract-retryable-type, error-contract-recovery-required, error-contract-recovery-empty, error-contract-recovery-min-words Error contract rules
Error contract (conformance) error-contract-conformance, error-contract-prefer-fail Error contract rules
Enrichment enrichment-type, enrichment-empty, enrichment-field-type, enrichment-output-collision, enrichment-prefer-block, enrichment-trailer-render, enrichment-trailer-orphan, enrichment-trailer-unknown-field, capped-list-no-truncation Enrichment rules
server.json ~40 rules prefixed server-json-* server.json rules

Read the full file on GitHub · 984 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 3d ago Changed cf57d7e35c3a
  2. 9d ago First seen · 984 lines · 86 tokens per session scan A 8f2c3de62558

Subscribe to this mod's changes

api-linter is a skill published in the GitHub repository cyanheads/obsidian-mcp-server (674 stars, last pushed 4d ago), licensed Apache-2.0. It adds 86 tokens to every session and 12,812 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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