replace_image_block

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

The annotations already declare a destructive, open-world, non-read-only operation. The description adds genuinely new behavioral context: the new block occupies the old position, the old block is deleted, and the block ID changes, which is an important consequence for any later references. This goes beyond what the annotations provide, though it does not mention permissions or failure behavior.

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 short, with the purpose stated first, followed by the most important consequence (block ID changes), and then a structured Args list. Every sentence earns its place. The only minor flaw is the slightly awkward line break in the prose section.

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?

The tool has an output schema, so return values need not be explained. For a three-parameter destructive operation, the description is complete enough: it covers purpose, side effects, and all parameters, including default behavior. The only missing piece is explicit guidance on when this approach should be chosen over its alternatives.

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 0%, so the description must carry the full burden, and it does: block_id is identified as the existing block to replace, file_path as a local path to the new image, and caption is explained with a default behavior (omit it to drop the old caption). That last detail is a meaningful semantic rule not captured by the schema's empty-string default.

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 ("Replace an existing image block's content") and names the source of replacement ("newly uploaded image"), which clearly contrasts with sibling tools like upload_image_as_block and find_replace_in_block, which operate on either new blocks or text within a block.

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 word "existing" implies the block must already be an image block, and the mention of a local file path implies an upload. However, the description never explicitly says when to use this instead of uploading a new block and deleting the old one or using find_replace_in_block, so the agent has to infer the boundary.

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