List instruments

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

Annotations already declare readOnlyHint=true (safe read) and openWorldHint=false (closed set). The description adds value by noting that missing symbols cause errors in other tools, and that replay sources return synthetic=true. This complements the annotations without contradicting them.

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?

The description is three sentences with zero wasted words. Each sentence serves a distinct purpose: stating the return value, explaining when to call and consequences, and describing the optional filter. Information is front-loaded with the core purpose first.

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?

Given the tool's simplicity (1 optional parameter, read-only, closed set), output schema exists, and annotations are clear, the description is fully complete. It covers purpose, usage guidance, parameter behavior, and edge cases (replay vs. live), leaving no gaps for an agent.

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% and already documents the group parameter syntax thoroughly. The description reinforces this by referencing the syntax explanation in the argument description, adding the context of how the filter interacts with the overall tool purpose, which is helpful for an agent.

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?

The description clearly states the tool returns 'every instrument this server exposes, with its digits and point size'. It uses a specific verb ('Return') and resource ('every instrument'), and distinguishes itself from siblings like get_quote and symbol_info by positioning itself as the authoritative source of symbol names.

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 advises 'Call this before anything else', warns that missing names cause errors elsewhere, explains the optional group filter's syntax, and clarifies behavior differences on replay sources. No alternative tools are needed for this purpose, and it sets clear prerequisites for using other tools.

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