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

Annotations already declare readOnlyHint=false, destructiveHint=false, idempotentHint=false and openWorldHint=false, so the safety profile is covered. The description still adds real value beyond them by disclosing the failure mode for pooled machines (404) and confirming that a grant record plus the machine record is returned.

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 sentences, no filler, with the core action and its main constraint front-loaded before the edge-case behavior.

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 mutation tool with no output schema, the description covers the effect, the return content and one key error condition. It stops short of noting permission requirements or what happens on a repeat grant given idempotentHint=false, which is the remaining gap.

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 all five parameters including format patterns and metadata limits. The description adds nothing about parameters and mildly conflicts with the schema by saying the machine is referenced 'by name' when the required parameter is machine_id (mch_...), not a name.

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 ('Lets a project's agent configs use one BYO machine'), and explicitly scopes it to BYO machines as opposed to pooled ones, which separates it from grant_pools_add and the grant_machines_* siblings.

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 'Pooled machines can't be granted this way and return 404' clause gives an explicit when-not condition and implicitly routes pooled-machine grants elsewhere, but it never names the alternative tool (e.g. grant_pools_add) the way a 5 would.

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