call_extension

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

Annotations already indicate destructiveHint=true, readOnlyHint=false, and idempotentHint=false. The description adds useful context beyond annotations: the target must be enabled and configured for externally_connectable, and the operation works without any open tabs. It does not spell out side effects, but the output schema and annotations cover the safety profile.

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 two short sentences with no filler. It front-loads the core action, then supplies necessary prerequisite context without wasting words.

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 required call, the description provides the target extension, message content, and key prerequisites such as enabled status and externally_connectable configuration. The optional session_id parameter and failure behavior are not described, but the presence of an output schema reduces the burden on the description.

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?

With 0% schema description coverage, the description compensates for extension_id and message_json by identifying the target as 'another installed extension' and the payload as a 'JSON message.' However, session_id is not explained at all, leaving an optional parameter without semantic guidance.

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: 'Send a JSON message from the BTAP extension service worker to another installed extension.' It clearly distinguishes this from sibling tools like list_extensions or set_extension_enabled, which manage extension state rather than communicate with an extension.

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 gives explicit prerequisites for use: the target extension must be enabled and must list this BTAP extension in externally_connectable. It also notes that it 'Works with no tabs open,' providing clear context. It does not explicitly name an alternative or say when not to use it, though no direct sibling offers the same capability.

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