get_performance_metrics

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

The description only states that it returns data, implying a read-only operation, but provides no behavioral details such as whether it requires a session, how it handles errors, or what happens if no metrics are available. With no annotations, the description carries the full burden and falls short.

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 a single sentence, which is concise and front-loaded, but it is arguably too minimal. While it avoids verbosity, it sacrifices necessary detail, earning a middle score.

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 (not shown), which reduces the burden to describe return values. However, the lack of parameter documentation and usage guidance leaves gaps. For a simple tool with one optional param, the description is barely adequate.

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?

The single parameter 'session_id' has no description in the schema (0% coverage) and the tool's description does not mention it at all. The agent receives no information about when or why to provide a session ID, making the parameter effectively opaque.

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 returns 'page performance timing data', which distinguishes it from siblings like get_network_logs or get_console_logs that return different data types. However, it lacks specificity about what timing metrics are included (e.g., load time, first paint), preventing a score of 5.

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?

No guidance is provided on when to use this tool versus alternatives. For example, it doesn't clarify that this tool is for performance metrics rather than network logs or DOM state, leaving the agent without decision support.

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