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Describe an instrument

describe_asset
Read-onlyIdempotent

What one instrument is and how it has done, in aggregate.

An equity, ETF, fund or bond, by id from ``find_assets``. Returns return,
annualised return, volatility and maximum drawdown over the standard windows,
the six factor tilts against the universe and a few company fundamentals, all in
the client's currency including the exchange rate. No prices or raw data.

A section that does not apply (factor tilts for a fund, a 3Y window for a recent
listing) comes back absent with the reason; absent means unknown, not zero. It
describes the instrument and makes no recommendation. Several instruments at
once, such as a screen's companies, are one ``describe_assets`` call.

The card charts the return since the first price, against a comparison the
client picks. The points stay out of the result unless ``series_in_context``
asks for them.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "asset_id": "<asset_id>"
    },
    "name": "describe_asset"
  }
}

Input Schema

NameRequiredDescriptionDefault
asset_idYes
series_in_contextNo

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observed

TDQS

A4.8/5.0
Behavior5/5

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

Annotations already cover read-only/idempotent/non-destructive, and the description layers on substantive behavior: the result is in client currency with the exchange rate, missing sections come back absent with a reason and absent means unknown not zero, and no recommendation is produced. The explicit handling of absent-but-not-zero sections is exactly the kind of nuance annotations cannot convey.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Purpose is front-loaded in the first sentence and each paragraph adds a distinct facet (scope, outputs, absent-section semantics, batching, chart/series behavior). Slightly long for a two-parameter tool, with the card-rendering sentence being the least essential for invocation.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

There is no output schema, and the description compensates by enumerating the returned metrics, the currency/exchange-rate treatment, and the semantics of missing fields. An agent has enough to call it correctly and to interpret the response without further documentation.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 0%, so the description carries the load and does most of it: asset_id's provenance and accepted asset classes (equity, ETF, fund, bond) are stated, and series_in_context is explained as the switch that adds chart points to the result. It stops short of describing id format/validity behavior, leaving a small gap.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

Opens with a concrete verb+resource+scope: 'What one instrument is and how it has done, in aggregate.' It enumerates the exact outputs (return, annualised return, volatility, maximum drawdown, six factor tilts, fundamentals) and explicitly contrasts with the sibling describe_assets for multi-instrument cases, so an agent can route without opening either schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Names the prerequisite sibling ('by id from find_assets') and the alternative ('Several instruments at once ... are one describe_assets call'), and states the condition that selects it. It also sets expectations on what is out of scope ('No prices or raw data'), which steers the agent away from using this for price series.

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

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