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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so safety is covered. The description adds useful context beyond that: it discloses the authentication requirement ("Requires a PJM API key") and states what is returned (each feed's name and metadata), which annotations do not convey.

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?

Four tight sentences, front-loaded with the core purpose followed by return content, usage guidance, and the auth prerequisite. No sentence is redundant and each earns its place.

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 read-only catalog tool with full annotation coverage and no output schema, the description covers purpose, return content, and auth need. Its one omission is that it never mentions the "feed" parameter's escape-hatch capability to fetch any feed directly, though the schema documents that fully.

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 100%, so the schema already documents all four parameters including the important "feed" escape hatch. The description itself adds no parameter-level detail, so baseline 3 is appropriate when structured fields do the heavy lifting.

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 (List) and resource (feeds published by PJM Data Miner 2), and scopes it as the catalog of every market-data dataset, enumerating examples (LMPs, load, generation, ancillary services, capacity, transmission). An agent can distinguish this discovery/catalog role from the dedicated siblings like pjm_lmp_realtime and pjm_load_forecast without opening any schema.

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?

Explicitly says when to use it: "Use to discover what PJM data exists before querying it," which positions it as a precursor to the feed-specific tools. It gives clear context but does not name the alternative dedicated tools (e.g. pjm_lmp_realtime) as the follow-up step, so the routing is implied rather than spelled out.

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