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

Annotations indicate readOnlyHint=false, destructiveHint=false, idempotentHint=false. The description adds meaningful behavioral context: a closed GRN can no longer take lines, discrepancies are treated as resolved, and closing never mutates the PO. This goes beyond the annotations and clarifies side effects. It doesn't mention reversibility or whether closing is permanent, but the provided details are valuable.

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 sentences, each earning its place: the action, the consequences, and the non-mutation guarantee. Front-loaded with the primary action. No wasted words.

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 single-parameter tool with no output schema, the description covers the action, side effects, and a key non-effect (PO not mutated). It doesn't state whether closing is reversible or what the response contains, but given the simplicity and the annotations, it is reasonably complete.

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%, so the schema already documents the 'grn' parameter as an open GRN id with an example. The description adds the context that the GRN must be open, which aligns with the schema's 'Open GRN id'. This is a baseline 3 because the schema carries the parameter documentation.

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 clearly states the action ('Close an open GRN') and the resource (GRN), and distinguishes it from siblings by specifying what closing means: no longer takes lines and discrepancies are treated as resolved. This differentiates it from grn_get, grn_list, grn_add, etc.

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 description implies when to use it: when a GRN is open and needs to be closed. It also states what closing does (no more lines, discrepancies resolved), which helps an agent decide. It doesn't explicitly name alternatives or say when not to use it, but the context is clear enough.

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