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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, so the base safety profile is covered. The description adds real context beyond that: the narrative block must be quoted directly with attribution to DC Hub under CC-BY-4.0, and the composite_score is 'verdict-aware.' No contradiction with the annotations — the read-only/idempotent hints are fully consistent with a retrieval tool.

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?

Three dense sentences, front-loaded with the core verdict/score outputs before the narrative and routing guidance. Every clause earns its place — output fields, citation requirement, when-to-use, when-not-to — though it runs longer than strictly necessary for a one-parameter read tool. The 'ONE market in depth' closer slightly repeats the opening 'single market' but serves sibling differentiation.

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 one-parameter, read-only tool with an output schema and 100% schema parameter coverage, nothing material is missing: returned fields, narrative/citation behavior, market coverage (300+ markets, 10 ISOs), and exclusions naming specific sibling tools are all present. The output schema relieves it of explaining return values, and it uses that headroom for routing guidance.

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%: market_slug is documented with concrete examples (northern-virginia, dallas, phoenix) and the source of valid slugs (rank_markets / get_market_dcpi_rank). With the schema carrying the full parameter documentation, the baseline of 3 applies; the description adds no extra syntax or format detail on top of it.

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: returns the DCPI rank for ONE market, listing the exact fields returned (BUILD/CAUTION/AVOID verdict, composite_score, excess_power_score, constraint_score, time_to_power_months) plus a narrative block. It distinguishes itself from siblings by name — rank_markets and compare_isos are called out as the multi-market/multi-ISO counterparts, and it closes with 'this is ONE market in depth.'

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?

Explicit when-to-use: 'Use to answer "should I build here?" with structured reasoning + ready-to-cite prose.' It also gives an explicit when-not-to with named alternatives: 'Do NOT use to rank many markets at once (use rank_markets) or to compare ISO grids (use compare_isos).' This is the full when/when-not/alternative pattern with nothing left to inference.

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