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

Annotations are sparse (readOnlyHint false, etc.), so the description carries the behavioral burden. It adds valuable context: the over-tolerance gate applies to cumulative received counts across all GRNs, and it mentions the free tier and full CRUD. This goes beyond the schema and helps the agent understand side effects. However, it doesn't mention whether the operation is idempotent or what happens to existing data, but given the annotations, the provided context is above average.

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?

The description is concise: three sentences, no filler, and the key context (batch usefulness, over-tolerance) is front-loaded before the free tier note. 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?

Given the tool's moderate complexity (6 params, 3 required) and rich annotations (though limited), the description covers the purpose, batch usage, and a key constraint (over-tolerance). It lacks explicit mention of return behavior, but there is no output schema, so it might be expected. Still, for an agent to call it, it is mostly 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 coverage is 100%, and the output schema is absent. The description does not add detail beyond what the schema provides for parameters, but with complete schema coverage, the baseline is 3. The description's focus is on the action, not on parameter specifics, which is acceptable.

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 states a clear action ('Add') and a resource ('line to an existing open GRN'), with a helpful qualification about adding units to an already-open line. It distinguishes the operation from general GRN creation (grn_add) but does not explicitly name sibling tools, so it's clear but lacks explicit sibling differentiation.

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 identifies the use case: handling batches of one delivery. It doesn't explicitly say when not to use it or name alternatives, but the phrase 'Useful when one delivery arrives in batches' provides clear context for when this tool is appropriate versus others like grn_add or grn_close.

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