Crawlora MCP

substack_user

Read-only

Get a public Substack writer profile by handle: identity, the publications they write for, their publicly visible subscriptions, and every subscriber signal Substack publishes. total is opt-in per writer and rounded to roughly three significant figures; when hidden, total_hidden is true and total is 0, which does not mean zero subscribers. paid_rough, paid_rough_int, and paid_tier are buckets -- no exact paid subscriber count is published. follower_count is exact but counts followers, not subscribers.

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": {
      "handle": "<handle>"
    },
    "name": "substack_user"
  }
}

Input Schema

Name	Required	Description	Default
`handle`	Yes	Required Substack profile handle, e.g. pragmaticengineer. Numeric user ids are not accepted by the upstream.

Output Schema

Name	Required	Description	Default
`data`	Yes	The tool result payload (shape varies per tool; see each tool's docs resource).

Schema Changelog

Changes observed during successful MCP inspections.

First observedOct 5, 2026

TDQS

A4/5.0

Behavior5/5

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

Annotations already declare readOnlyHint and openWorldHint, but the description adds substantial semantic disclosure: total is opt-in and rounded to ~3 significant figures, hidden totals show total_hidden=true with total=0 that 'does not mean zero subscribers', and paid counts are buckets rather than exact values. This is exactly the kind of field-level behavior an agent cannot infer from annotations alone.

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?

Front-loads the purpose, then spends the remaining text on genuinely load-bearing field semantics (rounding, hidden-total trap, bucket fields) rather than filler. It is dense but every clause about subscriber signals earns its place; the one long paragraph could be split for readability.

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

Completeness5/5

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

An output schema exists, so return values need not be described, yet the description goes further and warns about the misleading zero-total case and bucket fields. For a single-parameter read tool with full schema coverage and annotations, nothing needed to call it correctly is missing.

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% with a single documented 'handle' parameter, so the baseline is 3. The description restates that lookup is 'by handle' but adds no format or constraint detail beyond the schema's own note that numeric ids are rejected.

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

Purpose5/5

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

States a specific verb and resource ('Get a public Substack writer profile by handle') and enumerates the payload scope: identity, publications, subscriptions, and subscriber signals. It is clearly distinguishable from siblings like substack_publication (publication-centric), substack_user_search (lookup), and substack_user_activity (activity feed).

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?

The description explains what data comes back but never says when to choose this tool over siblings such as substack_user_search, substack_user_activity, or substack_user_connections. Usage is only implied by the handle-based framing; no exclusions or prerequisites are stated.

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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