st.chat.message.append

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

With no annotations, the description carries the disclosure burden. It states the core behavior of appending, highlights the mandatory confirm:true value (not visible in the schema's required array), and explicitly says content is not generated. It omits details like side effects or return shape, but the central behavior is transparent.

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?

A single, front-loaded sentence captures the purpose and key constraints with no filler. The clause 'caller-provided' earns its place by separating this tool from message-generation flows.

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?

This is a mutation tool with six parameters, zero schema descriptions, and no output schema. The description leaves required parameters semantically unexplained and omits behavior for force and snapshotLabel, so it is not complete enough for fully safe invocation without external docs.

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 description coverage is 0%, so the description must compensate. It clarifies 'message' (caller-provided) and 'confirm' (must be true), but says nothing about required parameters avatar and fileName, nor about the ambiguous force and snapshotLabel parameters. Several invocations would be guesswork based on property names alone.

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 opens with a specific action ('Append') and a resource ('chat transcript'), and clarifies the message is caller-provided rather than generated. This clearly distinguishes it from siblings like st.chat.message.edit or st.chat.message.delete and from content-generation tools.

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 gives an explicit precondition: confirm:true is required. It also states what the tool is not for ('does not generate message content'), which provides an implicit exclusion. However, it does not name alternative tools or explain when to prefer this over message editing or injection tools.

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