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

Annotations already tell the agent this is a non-read-only, non-destructive, closed-world mutation. The description adds the meaningful behavioral fact that pinning protects a revision from retention thinning, and that the same call with pinned=false removes that protection. It does not disclose error behavior for unknown artifact_id/rev_id or what the response contains, so it stops short of full transparency.

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?

A single sentence with the primary effect front-loaded and the reversal mode tucked into a parenthetical. No filler, no restatement of the title.

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-parameter, single-purpose mutation with no output schema, the description covers the core effect and the toggle. Remaining gaps are minor: missing failure behavior (nonexistent revision), permission implications, and confirmation of what state is returned.

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 only 33%: the schema documents 'pinned' as defaulting to true but leaves artifact_id and rev_id bare. The description adds real meaning for 'pinned' by equating pinned=false with unpinning, which the schema does not say. It still says nothing about how artifact_id and rev_id relate or whether rev_id is scoped to the artifact.

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 ('Pin a revision') plus the concrete effect: retention thinning will not remove it. This cleanly separates it from the deletion/read/write/history siblings in the artifact family. It falls short of 5 only because it does not name a specific alternative operation an agent might confuse it with.

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 parenthetical 'pinned=false unpins' tells an agent how to reverse the operation, which is useful implied usage context. However, there is no explicit when-to-use guidance, no statement of prerequisites (e.g., needing the artifact to exist or ownership rights), and no comparison to alternatives like artifact_delete or artifact_write.

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