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Equation 5 · Part 9 · How Tool Protocols and the Model Context Protocol Actually Work

subscript

at=πθ(ht∣Tt),ot=Call(at),ht+1=ht⊕(at, ot)a_t = \pi_\theta(h_t \mid \mathcal{T}_t), \qquad o_t = \mathrm{Call}(a_t), \qquad h_{t+1} = h_t \oplus (a_t,\, o_t)
subscript

What this part means

The lower label selects a particular version, component, or indexed member of the quantity. For example, x₀ and xₜ can be values at different positions.

Its job in the formula

A subscript distinguishes a version, component, step, or member of a quantity. It does not automatically mean multiplication.

The passage around this formula

It helps to write the whole loop down once, because the assumption buried in it is the one the rest of this article is about: at=πθ(ht∣Tt),ot=Call(at),ht+1=ht⊕(at, ot)a_t = \pi_\theta(h_t \mid \mathcal{T}_t), \qquad o_t = \mathrm{Call}(a_t), \qquad h_{t+1} = h_t \oplus (a_t,\, o_t). Here Tt\mathcal{T}_t is the tool set most recently returned by tools/list , each member carrying its own schema; πθ\pi_\theta is the model, which is expected — but not forced by anything outside its own training — to emit a call ata_t whose name and arguments validate against some tool in Tt\mathcal{T}_t ; Call\mathrm{Call} is dispatch through the client to the server and back, exactly as described above; and ht+1h_{t+1} is the context the model reasons over on the next step, built by appending the call and its result to what came before. The assumption is in…

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Learn the underlying idea

A subscript is a label attached below a symbol. It often selects a time step, component, category, or member of a sequence.

Open the illustrated subscripts: which member of a family? guide →

Sources cited in the article section

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