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

With readOnlyHint=false and destructiveHint=false already declared, the description adds the reassuring scope guarantee that all other subjects are left untouched, which is genuine behavioral context. It stops short of covering failure modes such as a duplicate name or an unknown id, and says nothing about permissions or undo, so it is strong but not complete.

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?

Three short sentences, zero padding, and the primary add/rename distinction is front-loaded before the convention and the alternative-tool caveat. Every sentence earns its place.

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 tool with no output schema and safety already covered by annotations, the description supplies the mode switch, naming convention, and sibling routing. It leaves open what happens on a duplicate name or an invalid id, which is the one remaining gap an agent would want before calling.

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 the baseline is 3, but the description adds meaning the schema does not: omitting id means create, supplying id means rename, and name should mirror the business's own spelling. Only sort_order goes undiscussed in the prose.

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?

"Add a subject, or rename one (give its id)" states a specific verb and resource and disambiguates the two modes of the single tool in one clause. The following phrase "every other subject stays" bounds the blast radius, and the sibling merge_subjects is named explicitly, so an agent can separate this from neighbouring subject tools.

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?

Explicit routing rule: if there are two spellings of one subject, use merge_subjects instead of renaming. It also gives a positive convention (use the business's own spelling verbatim), which is real operational guidance rather than restated mechanics.

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