substack_user

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

With no annotations, the description carries the full burden of behavioral disclosure. It thoroughly explains the quirks: total is opt-in, rounded to ~3 significant figures, total_hidden indicates hidden and total=0 must not be read as zero; paid_rough, paid_rough_int, paid_tier are buckets with no exact count published; follower_count is exact but counts followers, not subscribers. This is rich, honest context that prevents misinterpretation.

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?

The description is moderately long but every sentence adds value. It front-loads the main purpose and content, then explains data quirks in a logical sequence. It's dense and well-organized without redundancy. Slightly verbose in the middle section, but overall efficient.

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?

With no output schema, the description must explain return values, and it does: it lists the profile components and clarifies the tricky fields. It covers the main things an agent needs to interpret the result correctly. It doesn't address error cases (e.g., nonexistent handle) or pagination, but those are minor for a single-profile tool and the core information is complete.

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 single parameter 'handle' has a schema description 'Substack profile handle' which is fully covered (100% schema coverage). The tool description doesn't add any extra meaning about the format, source, or validation of the handle. For a simple identifier parameter, the baseline of 3 is appropriate; the description neither helps nor hinders.

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 opens with a specific verb and resource: 'Get a public Substack writer profile.' It then enumerates exactly what the profile contains (identity, publications, subscriptions, subscriber signals), making it unambiguous what the tool does. This clearly distinguishes it from sibling tools like substack_user_search, substack_user_connections, or substack_publication, even though those aren't explicitly named.

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?

No explicit guidance on when to use this tool versus alternatives. The description implies you need a handle but doesn't state that this is for retrieving a specific profile by handle, nor does it mention that substack_user_search exists for finding handles. No exclusions or conditions are given.

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