Skip to main content
Glama
wkbaran

Substack Reader MCP

by wkbaran

Search a publication

search_posts
Read-only

Search a specific publication's archive for posts matching a keyword. Enter publication and query to retrieve results.

Instructions

Search one publication's archive by keyword.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
limitNo
queryYes
publicationYesPublication name, subdomain, or URL.

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv0.2.0

TDQS

B3.1/5.0
Behavior3/5

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

Annotations already declare readOnlyHint=true and openWorldHint=true, and the description does not contradict them. The phrase 'archive' adds scoping context, but the description does not disclose result ordering, pagination, matching semantics, or whether live content is excluded. Since the annotations carry the safety profile, the description adds only modest behavioral context.

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

Conciseness5/5

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

The description is a single front-loaded sentence with no filler, repetition, or irrelevant detail. It states the action, scope, and input type efficiently.

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

Completeness3/5

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

For a straightforward read-only search, the schema plus description may be enough to construct a basic call. However, there is no guidance on choosing this tool among many similar siblings, no mention of expected output, and no output schema to fill that gap. Completeness is adequate but not strong.

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

Parameters2/5

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

Schema description coverage is only 33%: publication is described, while query and limit are not. The description's 'by keyword' maps to the query parameter, but it does not clarify the limit parameter or otherwise compensate for the low coverage. This is below the baseline expected when the schema leaves most parameters undocumented.

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?

The description uses a specific verb ('Search') and identifies the resource ('one publication's archive') and the method ('by keyword'), so an agent can recognize it as a scoped keyword search. However, it does not explicitly name or contrast sibling tools, so differentiation is implicit rather than stated.

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?

There is no guidance on when to use search_posts versus get_feed, get_recent_posts, or read_post, and no exclusions or prerequisites are mentioned. The only usage signal is the verb and scope in the description, which is implied rather than explicit.

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