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nws-weather-mcp-server: Instructions file for Claude Code

AGENTS.md

nws-weather-mcp-server AGENTS.md is an instructions file for Claude Code, Codex, OpenCode from cyanheads/nws-weather-mcp-server. It costs 5,787 tokens per session, scanned A, original, Apache-2.0.

A repository guide for the nws-weather-mcp-server, an MCP server that connects coding agents to the US National Weather Service API. It documents the server's coordinate-based workflow, units, caching, alerts, and project conventions.

In plain words
What is it for?
Use it when developing or maintaining this weather server, including forecast, observation, alert, caching, formatting, and API-request work.
Why use it?
It explains constraints such as the required User-Agent header, coordinate-only requests, and the need to follow URLs returned by the API rather than constructing grid endpoints manually.

Instructions file for Claude CodeCodexOpenCode

Written for Claude Code and Codex and OpenCode: Claude Code plugin machinery, but also the file is AGENTS.md. Also seen: reads .claude/ paths; mentions CLAUDE.md; mentions subagents.

This is cyanheads/nws-weather-mcp-server's own configuration. It tells Claude Code, Codex and OpenCode how to work on nws-weather-mcp-server itself, so it is not a mod to install elsewhere. Copy it as a starting point and replace the rules that are about this project. Everything nws-weather-mcp-server configures →

not rated 1repo changed 4d ago A scan 5,787 tokens original Apache-2.0
View source ↗ cyanheads/nws-weather-mcp-server npmjs.com
Reuse

Borrowing it

Nothing to install: this file belongs to cyanheads/nws-weather-mcp-server. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file
curl -O https://raw.githubusercontent.com/cyanheads/nws-weather-mcp-server/main/AGENTS.md
Clone the repo
git clone --depth 1 https://github.com/cyanheads/nws-weather-mcp-server

Made for: Claude Code, Codex, OpenCode.

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Per session 5,787 This file is loaded in full into every session.
When invoked 5,787 The same file — it is already loaded in full.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
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 $0.05787 $0.05787
Opus 5 $0.02893 $0.02893
Sonnet 5 $0.01157 $0.01157
Haiku 4.5 $0.00579 $0.00579

Measured 4d ago against content hash dff2ba48416b, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade A, and why

nws-weather-mcp-server AGENTS.md 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 4d 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

1 near-identical copy found in the catalogue:

AGENTS.md · 408 lines

How it starts

The opening of the file, as written. The whole thing — 408 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Agent Protocol

Server: nws-weather-mcp-server Version: 0.9.2 Framework: @cyanheads/mcp-ts-core

Read the framework docs first: node_modules/@cyanheads/mcp-ts-core/CLAUDE.md contains the full API reference — builders, Context, error codes, exports, patterns. This file covers server-specific conventions only.

Domain

Full design in docs/design.md. Key constraints:

  • API base: https://api.weather.gov — no auth, but requires a User-Agent header (403 without it).
  • Coordinate-centric: Most workflows start with GET /points/{lat},{lon}, which returns a grid cell with URLs for forecast, hourly forecast, observation stations, and zones. This is the routing layer — follow the returned URLs rather than constructing grid endpoints manually.
  • Grid caching: /points responses are highly cacheable (grid cells don't change). Cached in-process via a Map with 1h TTL — grid cells are geography, not tenant data.
  • Units are metric: Temperature in Celsius, wind in km/h, pressure in Pa. Convert to readable format in format() (show both F/C, mph, inHg/hPa).
  • No geocoding: API is coordinates-only. Tools accept lat/lon directly.
  • Alert quirks: /alerts/active has no limit param (returns 400) and no upstream cursor. Filter by area/severity, then window the fetched array locally.
  • Transient 500s: Grid forecast endpoints occasionally fail. Retry with backoff.
  • Hourly = 156 periods: Handler windows returned periods to 48 so structuredContent and content[] share the same bounded set; pre-page total + truncation notice surfaced via enrichment.
  • Paging is local windowing, never upstream. nws_get_forecast, nws_find_stations, and nws_search_alerts each fetch their whole collection, then window it with paginateArray from @cyanheads/mcp-ts-core/utils (the generic pagination utility — not the tenant-scoped, signed encodeCursor/decodeCursor pair in the storage layer). Each takes an opaque cursor input and surfaces nextCursor as enrichment, omitted on the last page per the MCP spec, so the Zod field is .optional() and never .nullable(). A bad cursor surfaces as -32602 InvalidParams from decodeCursor — leave it; do not convert it to a declared errors[] reason. Nothing caches the fetched collection (only /points grid resolution, 1h), so pages are contiguous within one response and not across separate calls: never document or promise a cross-call no-gap/no-overlap guarantee, least of all for alerts.

Read the full file on GitHub · 408 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. 4d ago Changed dff2ba48416b
  2. 9d ago First seen · 408 lines · 5,787 tokens per session scan A 0ad112465b80

Subscribe to this mod's changes

nws-weather-mcp-server AGENTS.md is an instructions file published in the GitHub repository cyanheads/nws-weather-mcp-server (1 stars, last pushed 5d ago), licensed Apache-2.0. It adds 5,787 tokens to every session, about $0.0289 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 2026-08-31.

alertsforecastmcpmcp-servermodel-context-protocolnational-weather-service
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