docs: document the available tools on hedera mcp server

### 1. **`query_docs_filesystem_hedera`**

> Run a read-only shell-like query against a virtualized, in-memory filesystem rooted at / that contains ONLY the Hedera documentation pages and OpenAPI specs. This is NOT a shell on any real machine — nothing runs on the user's computer, the server host, or any network. The filesystem is a sandbox backed by documentation chunks.
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> This is how you read documentation pages: there is no separate "get page" tool. To read a page, pass its .mdx path (e.g. /quickstart.mdx, /api-reference/create-customer.mdx) to head or cat. To search the docs with exact keyword or regex matches, use rg. To understand the docs structure, use tree or ls.
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> Workflow: Start with the search tool for broad or conceptual queries like "how to authenticate" or "rate limiting". Use this tool when you need exact keyword/regex matching, structural exploration, or to read the full content of a specific page by path.
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> Supported commands: rg (ripgrep), grep, find, tree, ls, cat, head, tail, stat, wc, sort, uniq, cut, sed, awk, jq, plus basic text utilities. No writes, no network, no process control. Run --help on any command for usage.
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> Each call is STATELESS: the working directory always resets to / and no shell variables, aliases, or history carry over between calls. If you need to operate in a subdirectory, chain commands in one call with && or pass absolute paths (e.g., cd /api-reference && ls or ls /api-reference). Do NOT assume that cd in one call affects the next call.
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> **Examples:**
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> tree / -L 2 — see the top-level directory layout
> rg -il "rate limit" / — find all files mentioning "rate limit"
> rg -C 3 "apiKey" /api-reference/ — show matches with 3 lines of context around each hit
> head -80 /quickstart.mdx — read the top 80 lines of a specific page
> head -80 /quickstart.mdx /installation.mdx /guides/first-deploy.mdx — read multiple pages in one call
> cat /api-reference/create-customer.mdx — read a full page when you need everything
> cat /openapi/spec.json | jq '.paths | keys' — list OpenAPI endpoints
> Output is truncated to 30KB per call. Prefer targeted rg -C or head -N over broad cat on large files. To read only the relevant sections of a large file, use rg -C 3 "pattern" /path/file.mdx. Batch multiple file reads into a single head or cat call whenever possible.
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> When referencing pages in your response to the user, convert filesystem paths to URL paths by removing the .mdx extension. For example, /quickstart.mdx becomes /quickstart and /api-reference/overview.mdx becomes /api-reference/overview.

### 2. **`search_hedera`**

> Search across the Hedera knowledge base to find relevant information, code examples, API references, and guides. Use this tool when you need to answer questions about Hedera, find specific documentation, understand how features work, or locate implementation details. The search returns contextual content with titles and direct links to the documentation pages. If you need the full content of a specific page, use the query_docs_filesystem tool to head or cat the page path (append .mdx to the path returned from search — e.g. head -200 /api-reference/create-customer.mdx).