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

Annotations already indicate mutation and destructiveness, but the description goes beyond them by disclosing that the image is center-cropped to a square and scaled to at most 640x640, that the previous photo cannot be restored, and that contacts may see the old photo for a while due to caching. These are valuable behavioral details not present in structured metadata.

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 four sentences, each serving a distinct purpose: stating the action, explaining the replace path with transformation details, explaining the remove path, and disclosing consequences. There is no filler or repetition.

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 3-parameter tool with an output schema, the description covers the two usage modes, constraints (format, size, scaling), and non-obvious effects (irreversibility, eventual consistency). Nothing an agent needs to call the tool correctly is missing.

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%, so the baseline is 3. The description adds contextual meaning beyond the schema by clarifying that the photo is what every contact sees and by highlighting the irreversible consequence of replacing/removing it. This enriches the parameter definitions without contradicting the schema.

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: "Change the profile photo of one of your own WhatsApp accounts — the picture every contact sees." It clearly distinguishes the tool from siblings like wa_get_profile and wa_set_presence by scoping it to one's own account profile photo.

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 provides clear context for when to use the tool: changing one's own profile photo, with two explicit invocation modes (pass image_base64 to replace, or remove=true to delete). It does not explicitly name alternatives or exclusions, but no sibling tool performs this function, so the context is sufficient.

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