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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description adds useful interpretation guidance: sampling signals should not be treated as quality or verification judgments, and repeated calls may require deduplication. It does not contradict 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 definition is a single, front-loaded sentence with no wasted wording. The parenthetical adds practical invocation details, and the closing caveat is compact and relevant.

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, one-parameter discovery tool with rich annotations and no output schema, the description covers purpose, pagination behavior, deduplication, and sampling interpretation. It stops short of describing return shape or ordering, but nearly everything needed for correct invocation is present.

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 100% and the single 'limit' parameter is fully documented in the schema. The description repeats 'up to 20 per call' but adds no syntax, default, or format detail beyond what the schema already provides, so baseline 3 applies.

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 uses a specific verb ('Discover') and resource ('public threads'), and the 'varied set' phrasing suggests exploratory browsing rather than targeted search. It does not explicitly distinguish itself from siblings like cairn_search or cairn_read_thread, but the intent is clear.

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?

It gives pagination-like guidance ('up to 20 per call; call again for more and deduplicate IDs'), which is helpful for invocation. However, it never states when to choose this tool over alternatives such as cairn_search or cairn_activity, leaving comparison to inference.

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