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

Annotations already cover readOnly, idempotent, openWorld, and non-destructive. The description adds real behavioral context beyond them: an API-key auth requirement and the five-minute real-time cadence that tells the agent how fresh the data is. It doesn't describe rate limits or failure behavior, so it isn't a 5.

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?

Front-loaded with what the tool returns, then use cases, then the auth requirement. Mostly tight, though the grid-size aside (13 states, ~65M people) is flavor rather than actionable detail.

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?

With no output schema, the description helpfully names the returned price components (total, congestion, marginal loss) and the EPT datetime filters are covered in the schema, so an agent knows enough to call it correctly. Missing return format details like row ordering keep it from a 5.

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 all five parameters are already documented, which sets the baseline at 3. The description's mention of node filtering and the Western Hub example loosely mirrors pnode_name/pnode_id but adds no syntax or format detail beyond 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?

States a specific verb+resource with scope: real-time five-minute locational marginal prices by pricing node, including the total, congestion, and marginal-loss components. This clearly separates it from siblings like pjm_load_forecast, pjm_generation_fuel_mix, and pjm_feeds.

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?

Gives concrete trigger phrasings ("PJM power price right now", "PJM Western Hub price", "which PJM nodes are congested") and states the prerequisite of a PJM API key. It stops short of explicitly naming which sibling to use instead when the agent wants load or fuel-mix data.

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