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

Annotations already declare readOnly/idempotent/non-destructive, and the description goes well beyond them: unknown areas raise an error naming nearest matches (and should be read back), provenance.pub_freq reveals the grain the pipeline judged resolvable, and inc_se_pp carries the per-period standard error of the move. It also notes the series is smoothed toward the parent geography and is free to call.

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 the definition, base period and source, then the routing contrast, then argument semantics, then the provenance caveat. Dense and largely waste-free, though the three-paragraph shape is longer than strictly necessary and the trailing 'Free.' adds little.

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 an output schema present, return values need no explanation, and the annotations cover the safety profile. The description supplies addressing rules, the sold-vs-asking distinction, and the provenance/frequency caveat; only the method parameter and date/limit semantics are left uncovered.

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 0%, so the description must carry parameter meaning, and it does so thoroughly for area_code/area_type ('W14'+district, 'Camden'+lad, or NATIONAL) and partially for frequency via provenance.pub_freq. However it says nothing about the method enum (hedonic_smoothed vs hedonic_raw), start, end, or limit, leaving four of seven parameters to be inferred.

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 (hedonic ASKING-PRICE index) with its scope (postcode district, local authority, or Great Britain), its source (portal listings, Rightmove ~95%), its base (2022M01 = 100), and its output semantics ('value' is an index level, never a price). It explicitly distinguishes itself from the sold-price sibling market_index_series and from the levels sibling listing_market_series.

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 a concrete use case ('how have asking prices in W14 moved since 2022') plus the rationale for choosing it over the alternative: asking LEADS sold by months and includes stock that never sells, so use market_index_series for sold prices and listing_market_series for levels. It even names the condition that selects quarterly over monthly frequency.

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