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

Adds real context beyond the annotations: marking read removes the item from the feed, the operation is reversible ('unread again'), and the blast radius is limited to the caller's own read state with monitors and history untouched. That scope statement is exactly the kind of reassurance a write tool needs, though it says nothing about error behavior or what a missing checkId does.

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?

Two tight sentences with the primary action front-loaded and the scope caveat second. No filler, though the dense one-sentence enumeration of three modes takes a moment to parse.

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 three-optional-parameter state toggle with annotations and no output schema, the description covers the modes and the side-effect boundary adequately. The remaining gap is the precedence rule when all and checkId conflict, which neither schema nor description resolves.

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 100%, so all three parameters already carry descriptions. The description reinforces that checkId targets a single change and that the unread flag restores it, but adds no format or interaction detail (e.g., what happens if all and checkId are both supplied) beyond the schema. 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?

Specific verb (mark read) plus resource (feed item / whole feed) and it enumerates all three modes: read one, unread one, read everything. It does not distinguish itself from near-siblings like hide_change or get_feed, so an agent still has to infer the boundary, but the operation itself is unambiguous.

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 three modes imply when to use it, and 'omit with all: true' in the schema hints at the selection rule, but the description never states exclusions or names an alternative (e.g., hide_change vs. mark read). Usage is inferable rather than stated.

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