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

Annotations already declare a safe read (readOnlyHint/idempotentHint, non-destructive), so the remaining burden is on semantics, and the description delivers: null-vs-0 metric convention, platform-specific gaps (Threads has no reach, Bluesky only likes/comments/shares), X views mapped to impressions, inclusion of posts published outside Narrareach, and pagination via page.nextCursor.

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?

Front-loaded with the verb, resource, and scope, then flows into metric semantics and filtering. The enumerated metric list is slightly heavy, but nearly every clause carries operational meaning rather than restating the name or schema.

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?

An output schema exists, so return structure need not be described, yet the description still covers the non-obvious parts of the payload (metric nullability, per-platform differences, source attribution). Combined with filter and cursor guidance, an agent has everything needed to call it correctly.

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?

Schema coverage is 57%, and the description compensates well: it explains what 'source' means, that platform/source/from/to are filters on published time, and that pagination uses page.nextCursor from a prior identical-filter call. It adds little on limit or includeDeleted, which the schema already documents.

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?

States a specific verb and resource ('List the writer's own posts') plus the exact set of connected platforms, the ordering (newest first), and the metric payload. An agent can immediately tell this apart from list_scheduled_posts, list_inspiration_posts, and list_notes.

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?

Gives a clear exclusion ('Personal account only; Substack is covered by list_notes and get_platform_analytics') and explains how to narrow results via platform/source/date filters. It stops short of routing against other near siblings such as list_scheduled_posts or list_inspiration_posts, so it is strong but not fully exhaustive.

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