substack-mcp

get_posts_by_date_range

Retrieve Substack posts published between two ISO dates. Set start_date and end_date to filter a publication's archive by publication date.

Instructions

Get posts published within a date range

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "start_date": "<start_date>",
      "end_date": "<end_date>"
    },
    "name": "get_posts_by_date_range"
  }
}

Input Schema

Name	Required	Description
`limit`	No	Maximum number of results (default: 100)
`end_date`	Yes	End date (ISO 8601 format, e.g., 2024-12-31)
`start_date`	Yes	Start date (ISO 8601 format, e.g., 2024-01-01)

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.0.0Sep 13, 2026

TDQS

C2.9/5.0

Behavior2/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

No annotations are provided, so the description carries the full behavioral burden, yet it says nothing about ordering, pagination behavior, whether the range is inclusive, or permissions required. Beyond confirming it is a read-style retrieval, no behavioral context is added.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

A single tight sentence with no filler and the core scope front-loaded. It is efficient, though arguably under-specified rather than truly concise given the tool's complexity.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness2/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With no annotations, no output schema, and a default limit of 100, the description should clarify return shape and whether results are truncated, but it does neither. It is incomplete for an agent that needs to know what it gets back and whether to paginate.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so start_date, end_date, and limit are already fully documented in the schema (including ISO 8601 format and the default). The description adds nothing beyond the date-range concept already conveyed by the name, so the baseline 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb (Get) and resource (posts) with the scoping condition (published within a date range), so the agent knows it retrieves posts by publication date. It is distinguishable from list_recent_posts by the explicit date-range framing, though it never names or contrasts with any sibling.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

No when-to-use guidance, no exclusions, no mention of when search_posts or list_recent_posts would be preferable. The date-range constraint is implied by the name and description, but the agent must infer the selection criteria on its own.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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