Read a post

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

Annotations already carry the read-only and open-world hints; the description adds meaningful context by disclosing that paid posts are fully returned only when the account has access and that long posts are paged via a `start` cursor. It does not address failure modes, but it goes beyond the minimal annotation coverage.

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

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

Three sentences, with the core action front-loaded and each sentence earning its place by adding paywall or pagination behavior. There is no redundancy or filler.

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

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

For a read-only, single-resource fetch with a small parameter set, the description covers purpose, paywall access, and pagination. It omits explicit treatment of `format`/`max_chars` and error handling, but the enum and integer ranges are in the schema and the open-world annotation covers result volatility.

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

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

The description clarifies the `start` parameter's role in pagination, reinforcing the schema's character-offset note. However, `format` and `max_chars` have no schema descriptions and are not explained in the description, leaving a coverage gap at 50% overall.

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

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

The description states a specific verb ('Read'), a resource ('full content of a Substack post'), and a concrete output format (Markdown). This clearly distinguishes it from sibling list/search tools like get_feed and search_posts, and adds scope beyond the generic title.

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

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

The description implies when to use the tool ('full content' retrieval) but does not explicitly name alternatives or state when not to use it. The paywall note provides access conditions, but there is no direct routing guidance relative to siblings.

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