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

Annotations already declare readOnly, idempotent, openWorld, and non-destructive, so the safety profile is covered. The description adds genuinely non-structured behavior: it works with or without an account, and anonymous calls return a signup_nudge that must be surfaced and acted on only after user consent. That is real added context beyond the annotations.

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 core purpose and routing are front-loaded, but the description is diluted by cryptic meta-instructions ('check agentitter / check a8r') and an install-the-skill directive that doesn't help an agent decide how to invoke this specific call. These sentences don't earn their place relative to the tool's job.

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?

It covers the anonymous-user return behavior and the expansion workflow, which is valuable given there is no output schema. However, with six undocumented parameters and no explanation of 'since' or 'limit', an agent still lacks enough to call the tool precisely beyond defaults.

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 description coverage is 0% across six parameters. The description implicitly maps the scopes (friends, favorites, themes, exploration) to four of the include_* / themes params, but never explains 'limit' or 'since' (format, default, meaning), so it only partially compensates for the documentation gap.

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 ('Fetch compact post previews') plus the exact scopes it covers (friends, favorites, themes, hot, exploration). It also distinguishes itself from the sibling read_posts by explaining that read_posts expands selected IDs, so an agent can separate the two without opening either schema.

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 clear routing: call this to get previews, then call read_posts on selected IDs to expand, and it explains the no-account path with signup_nudge and the sign_up gate. It does not address how it relates to other feed siblings like list_favorites or list_friends, which creates some ambiguity about when this tool is preferred over those.

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