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

Annotations already indicate a mutation (readOnlyHint=false). The description adds useful behavioral detail: rendering as a clickable pill with hostname, and coordinate semantics via reference to add_text. It does not contradict annotations and provides context beyond what annotations offer.

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, front-loaded with the action and styling, zero redundancy. Every word contributes to purpose, usage, and coordinate rules.

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 add-tool with annotations covering safety profile and no output schema, the description adequately conveys what the tool does, when to use it, and coordinate behavior. It doesn't mention error cases or prerequisites, but these are likely inferred from the board context. Overall, it is sufficiently complete for an agent to invoke correctly.

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 only 17%, so the description must compensate. It explains x and y indirectly via 'Same coordinate rules as add_text', and url via 'URL capsule', but board_id, author, and access_key are not addressed. The reference to add_text provides some context, but not all parameters are clarified.

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 tool adds a URL capsule rendered as a clickable pill, and explicitly distinguishes it from add_text for link-only nodes. The verb 'drop' plus resource 'URL capsule onto the board' makes the purpose unambiguous.

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?

It explicitly says 'Use this instead of add_text when the node is just a link' and references coordinate rules from add_text, giving clear when-to-use guidance and an alternative. This goes beyond typical descriptions by naming the sibling tool and the exact condition.

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