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

Annotations already declare readOnlyHint=true and destructiveHint=false; the description adds useful context by explaining that existing rules are preserved and that 'the stance's version is reported instead of applied.' This clarifies the non-destructive, preview-like behavior beyond the annotations.

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 overloaded: it begins with a full JSON-RPC example for a sibling tool, then a long run-on sentence covering stances, behavior, and an example all at once. The core purpose is buried and the structure is not front-loaded for quick agent comprehension.

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 simple two-parameter tool with no output schema, the description covers the decision-relevant details: accepted stance values, the input robots.txt, the non-destructive merge behavior, and an example. It is complete enough, though the irrelevant 'FIRST CALL' block could mislead an agent.

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%, but the description adds meaning by listing the eight exact stance slugs and providing a concrete example with both parameters populated. This is valuable because the schema describes 'stance' only as 'one of the eight stance slugs' without enumerating them.

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 specific verb and resource: merge one of eight maintained robots.txt stances into an existing robots.txt. It is clearly distinct from lint/audit/diff siblings, though the opening 'FIRST CALL, needs nothing: ... no_arguments_lint_this_hosts_robots_txt' block muddies the focus by pointing at another tool.

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 phrase 'into a robots.txt you already have' gives a clear prerequisite and usage context, and 'without touching a single rule you wrote' implies when this tool is appropriate. However, it does not explicitly name alternatives or state when not to use merge_policy versus diff_robots_txt or lint_robots_txt.

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