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

Annotations already declare this is a non-destructive, idempotent, non-open-world mutation, so the safety profile is covered structurally. The description adds no context about what marking read actually changes (unread counts, digest state) or whether it is reversible, leaving a modest gap for a write operation.

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 short sentences, front-loaded with the action and followed immediately by the one disambiguation that matters. No filler, no restatement of the name.

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 values need not be described, and annotations cover the safety profile. Combined with the id guidance, the definition is sufficient to call correctly; only the downstream effect of the write is left unstated.

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 0% and the single parameter is just typed as string, so the description carries the full burden. It resolves the key ambiguity by naming the correct source of follow_opening_id and explicitly excluding the nested opening.id — the main way this call would fail.

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 concrete verb and resource: mark a single Following row as read. The word "one" implicitly contrasts with the sibling following.openings.mark_all_read, though it never names that sibling or inbox.mark_read explicitly.

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 an explicit sourcing rule for the input (take the id from following.openings.list, not the nested opening.id), which is exactly the mistake an agent would make. It does not, however, spell out when to prefer this over following.openings.mark_all_read.

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